I hate gardening. But I love having nice flowers. What I need is some recommendations for things that basically grow on their own.
For instance, in my neighborhood, growing wild, and in alleys, I see these cool purple flowers, and also some rather spectacular orange ones, blooming now. I think the orange ones are some kind of poppy. If they can grow in an alley, maybe they could stay alive in my yard.
Right now I have a couple hundred tulips that usually brighten up my yard in the summer, along with grape hyacinth that is trying to take over, but by this time of year that’s over.
I have roses–a wild one that blooms once, blooming now, and a few others that bloom twice. I do put in some maintenance on these roses. I deadhead them and keep the weeds out. Grudgingly.
I have a purple climbing thing, I think it’s a clematis, and some pink mallow that should be blooming soon.
But I need more color. I am really craving that purple and orange, and red is always good. Ideally something either in a bulb (that can be left in the ground always, unlike the dahlia that I dug up and then forgot to replant) or something that will reseed itself into perpetuity.
I seem to be in Zone 6b.
Bonus if someone can recommend something that likes a good hot spot, because I have a good hot spot. Southern exposure, up against a brick wall, and sheltered on all sides. I spend a lot of time there. Ideally the perfect plant(s) for this space would also smell good. I wouldn’t mind putting a little more effort into that area, it’s small, but I’m very streaky when it comes to remembering to do things to plants other than water. And by water, I mean make sure the automatic sprinkler system is functioning correctly.
Do geraniums grow there? I have Thumbs of Doom and geraniums are perfectly happy to grow for me. Lovely flowers, in many colors, long-living plants and the flowering season lasts months.
My favorite for this application are four o’clocks. They are perennials and can come back year after year. You plant the seeds in the spring and that’s pretty much it. They even produce seeds so you can grow more if you want.
As per their name, the blossoms open in the late afternoon, but the flowers are all over the plant and look nice even when they are closed.
The seed mixes contain colors like white, yellow and red.
I got some blooming right now and I haven’t done anything with them in years.
Never heard of four o’clocks, I’m gonna have to look into that.
What I do, is every couple of years, in fall, I get a bunch of different types of bulbs (that claim to bloom during different times of summer) and plant them all. Come Spring, they bloom, then die and repeat each year. If I feel like it (and the garden needs it), I’ll run to a garden store/Home Depot in early/mid summer and a few flats of annuals to stick in the ground. They only have to last a month or two, so it’s not like you have to do a particularly good job planting them, and they’re easy to rip out at the end of the season.
Sedum are good for hot dry. Daylilies are pretty no-brainers, and you can get a variety of colors and bloom times. And, of course, there are the familiar coneflowers and brown-eyed susans. Yeah, poppies would probably do well. But I have no experience gardening in Denver.
I have a son who lives in Denver. Impresses me as basically a high desert. I’d look towards natives, and consider xeriscaping. I’m sure sedum would do well.
Your best bet would be to walk around your neighborhood, and talk with folk who are digging in the dirt - and who have gardens you admire. Gardeners are generally quite happy to talk about their gardens, and are often happy to share their plants.
Get a package of Marigold Seeds. Lightly sprinkle the seed over an area of bare dirt. Use this $5 hand tool to scratch the seed into the dirt. It just needs to be lightly covered.
Keep damp for a couple weeks. You’ll see sprouts and they’ll grow quickly.
Each Marigold flower will drop at least a dozen seeds. They’ll come up even thicker year two.
I started this way with one pack of seed. I had Marigolds for ten years with no work. Just occasional watering.
[Moderating]
Since this is asking for advice, let’s move it to IMHO.
Is the purple-flowered plant mentioned by the OP dame’s rocket? That’s a dependably blooming plant that thrives on roadsides, along with another ancient European import (orange day lilies, Hemerocallis fulva “Europa”.
“Ordinary” pink Echinacea is very tough and returns each spring for many gardeners in your zone. Four o’clocks would probably be iffy at best in zone 6b, while being perennial further south (they can certainly be grown as annuals, or the tubers can be lifted in fall and stored in a frost-free place over the winter).
Perennial phlox is also an easy plant to grow. Typically people start out with one of the named hybrids, and over the years they revert to the original pink-flowered phlox (which is still nice).
Your local Walmart or Home Depot garden center will stock plants that will grow in the local area.
Spring is the best time to shop the garden center and look at the perennials.
Seed is easier. Always look at the seed rack for flowers that are easy. Avoid any that requires starting during the winter in a greenhouse. That’s a lot of trouble for a non-gardener.
I mentioned marigolds. There’s other self seeding flowers that are just as easy.
Here’s a list
You’re in Denver? Or somewhere in the Front Range?
You want drought tolerant plants, for sure. Ice plant comes in purple, yellow and pink, and will take off as a ground cover. Daylilies are pretty fool-proof, as someone said above. Poppies will self-seed, as will cosmos and echinacea. Autumn joy sedum is beautiful and lasts through the summer and into fall. Russian sage is purple and also lasts forever. Anything you plant will need to be watered to get it going, but once established should be fine.
Very well if you keep them watered. I keep them in largish terra cotta pots which I slip into slightly larger plastic pots that stay buried in the flower bed, water comes from a drip line set to a timer. When winter comes I bring the pots inside, switch out the dirt for something new and yummy, and store them in a crawl space under the house. Spring = bring out the pots, drop them into their plastic sockets and get them wet.
Sunflowers kick ass in hot spots and they don’t demand a ton of water. They attract half a dozen varieties of bees, including a brilliant green one I’ve only ever seen on sunflowers. And the birds get after the seeds in the early fall which is pretty cool.
Alternatively, aceplace57’s marigold idea is a good one. They just go nuts (which is awesome) but can look a little gangly toward the end of the season. Along the same lines, I also keep hanging pots of pansies, petunias, and some other things. Petunias come in a mind-boggling variety of colors and attract hummingbird moths at night, which must be seen to be believed. No maintenance apart from water. AND when the flower dries up, as they do, you can pull them off and drop them on the ground with a reasonable expectation of getting feral plants. Ferals are fun because they have the same color as the parent but the flowers tend to be smaller. So instead of big awesome blobs of color you get tiny sparks of random color.
Man, that impresses me as pretty much the OPPOSITE of “no fuss” plants sought by the OP! Hell, my wife and I are both avid gardeners, and neither of us would grow anything needing that kind of care.
My son just xeriscaped his tiny postage stamp backyard in Denver. Rocks don’t need to be watered or overwintered! 
Just tossing out an idea that works. If someone is looking for less fuss than drop in/pull out (drip line is optional) then I got nothin.
Morning glories. Plant them once, and they’ll come up from seeds every year like weeds. They bloom all summer.
Personally I like spider lilies, also known as surprise lilies. The flower comes up seemingly out of nowhere in late summer. Then the leaves come up and stay green throughout winter, soaking up sunlight and storing energy in the bulb, then the leaves wither away in spring. Which means they are dormant during spring and summer, so they can coexist with other annuals and don’t get in the way. Dows side is the short time frame of the flowers (they all bloom within a span of a couple weeks) and zone 6b may be marginal.
Geranium ‘Rozanne’ if you can get it. It’s a sterile hybrid, so it doesn’t set seed, it just goes on and on and on flowering for months, with blue-purple-pinky slightly colour changing flowers. I’m in a slightly milder zone, but ‘bung it in and forget it’ is all I ever did when I had it (I moved and left, it’s long living), and it always looked amazing. It dies back to the ground in winter, you don’t even need to tidy it up, it does it itself. It won the UK RHS ‘Plant of the Century’ award, and I can see why.
Only disadvantage is that it’s useless for pollinators as it doesn’t produce pollen or nectar, and it doesn’t smell of anything, I guess.
Cyclamen hederifolium is also a possible- it flowers late in the season (about when the geranium stops) into autumn. Purply pink flowers. That will self-seed, but it doesn’t go crazy and is only a little plant anyway, and dies back to a corm over spring and much of summer. It looks at its best when not much else does.
I can’t think of much other than shrubs and maybe climbing honeysuckle that would give you scent while being dead tough, and climbing honeysuckle does need cutting back every now and again or it’ll go a bit crazy. How much space for flowering shrubs would you have?
A mountainous Zone 6? No prob (I garden in a mountainous Zone 3). I agree with the day lily recommendation - I would also add asiatic lilies. In spite of the name (lily) bringing up images of fainting couches, day lilies and asiatic lilies are tough as nails and require only sun and whatever rainfall you get. The most maintenance you would have to do with them is divide the patch every five or six years when it gets too big. And they come in all kinds of gorgeous colours, including hot oranges.
Irises are also good, tough plants that require almost nothing from you. There are more colours of irises every year.
Columbines would work for you.
Salvia is another wonderful, low-maintenance plant for your purple pop.
Don’t be afraid to use foliage plants for three season colour, too. I use coral bells and shrubs for exactly that.
If you have the money, a landscape designer can make your yard into exactly what you want it to be. 
Marigolds are pretty straightforward, and many different varieties, Nasturtiums seem to be pretty easy as well
another benefit of four o’clocks is that Japanese beetles love to eat them…’
…why is that good? because the 4’s are also TOXIC to them, they’re lethal, the beetles eat them and then die, they’re the perfect trap crop, plant them away from the plants you want to protect, and let the beetles have a lethal feast
You might want to check with your area’s native gardening group - natives are more likely to handle your local conditions well, and support native fauna better.
Heirloom roses and earth-kind roses can be quite easy to grow. Roses have a reputation for being fussy, but that’s because most roses that are sold are heavily hybridized for showy blooms. Heirloom roses are roses that were “found” growing basically wild in abandoned homes, graveyards, or similarly untended locations. Best to find heirloom roses that were found in your area - they will be extremely hardy!
When I grew flowers, I liked cosmos because they were so easy to grow. It was just a matter of scratching in some seed, keeping the dirt slightly damp, and watching the cosmos spring up and bear pretty purple, hot pink and white daisy-like flowers. I’m pretty sure they’d do fine in Denver, and they like heat.
Added bonus: they make great cut flowers for arrangements.
Up here in New England, we have a wild rose variety that seems to be a crossbreed of Kudzu, cockroaches, and Tribbles, it is well beyond feral, and is everywhere, it is a creeping vine-type plant that grows inside other plants, using their branches as climbing trellises, and they will happily choke out the host plant
they’re incredibly prolific, and hard to get rid of once established, yes you can cut the vines down and pull them out, but they’ll regrow from the root ball next year, i’m sure these things would survive a thermonuclear detonation
you simply CAN’T kill these things, they’re extremely thorny, and the flowers aren’t even remotely attractive, small, boring white flower clusters