See title — what goes better with a tucked-in dress shirt? A V neck or crew neck T shirt? Are other colors than white acceptable? I’m not going for super formal here, more like business casual, I guess. No tie, maybe a jacket.
Crew all the way for me. I never really understood a V-neck unless you have your shirt unbuttoned to show more of your naked chest (presumably along with some necklaces).
I think the only difference is whether or not you have a bit of the collar of your undershirt visible above the top button (not counting collar button) of your dress shirt. I prefer V-neck so that I don’t have a bit of my underwear showing.
I go with v- necks but the downside is the V of the undershirt is almost always smaller than the V in the top shirt. I doubt one is more aetheticly pleasing than the other.
Usually a V-neck if I’m not wearing a tie. Not that I care that much if the T-shirt collar is visible, but I have a couple of white V-necks and I might as well use them for that. When I can’t find one of those V-necks I’ll wear a colored shirt, mainly black because I have so many. Something about an exposed white T-shirt collar under a dress shirt reminds me too much of the olden days.
With tie always a crew-neck. The V-neck of a V-neck undershirt always prints through and looks “finky” in my Dad’s unforgettable phrase when I was 11 or whatever.
Without tie always V-neck. You never want anyone see the undershirt. A recent challenge is modern v-necks aren’t always as large a V as in the old days. And modern casual shirts often have rather open necklines. If you can’t hide the V-neck undershirt completely under the outer shirt, don’t wear the undershirt at all.
The Fashion Fogey Hath Spoken!!! 
I have a hypersensitive gag reflex. If anything puts pressure on my throat, I start upchucking.
So, I always wear V-necks, and I buy dress shirts with the collar a half-inch larger than the fashion mavens consider proper.
If the tee shirt is underwear, always white, I would wear whatever doesn’t show under the outer shirt. If the tee shirt is part of the ensemble, white or with color, then I would always wear a crew neck. I think V necks look icky, so they may be worn but should never be seen.
Ha, I like that! Wish it was a TV show. 
Kinda like Queer Eye for the Straight Guy, but using Dr. Rick from the Progressive ads:
Except for the moustache and him weighing 40-50 lbs. more than me I’d make a decent stand-in for Dr. Rick. I don’t know whether to laugh or cry at that observation.
Tee shirt with a tie, top button buttoned. V-neck if the collar is open White with a button up dress shirt.
I wear tee-shirts under fleece pullovers. But that’s sort of what you do at altitude. Going to a memorial service for a coworker tomorrow. I will wear a button up shirt, and t-shirt underneath. The colors won’t clash. Anyone with a tie on will.
Neither. If I’m wearing a dress shirt, the only thing under it is me.
I too think V necks look dorky. Crew neck always, for white and black undershirts (the only colors I wear).
I wear Crew neck
V necks sag and twist on my body.
Crew neck only for me. White. Nice and tight at the collar.
So at least some of you folks are saying you wear a dress shirt with no tie and an open neck with your crew-necked white t-shirt showing? The 1950s called, they want your Dad’s fashion sense back.
Had this dilemma myself last night. Dress shirt in dark blue, no tie. I have v-necked undershirts in white with a large V or gray or black ones with a smaller V. Goal is to wear an undershirt that does not show through the dress shirt’s open neck.
Settled on the smaller v in dark gray. Which if I really tug it down just stays hidden. For a few minutes, then starts peaking out again. Sigh. Fortunately it was rather dark in the venue and my wife is used to my fashion malfunctions.
If it’s a white T-shirt you are correct. If it’s some other color it’s an act of rebellion and perfectly acceptable for being so. If you’re going to have a white T-shirt showing you need the whole uniform and also have a pocket protector in the shirt pocket. on top of pants that are too short exposing white socks and brown penny loafers.
With a short-sleeved checked “sport shirt”.
I don’t wear dress shirts often, and when I do, I wear a tie. And even if I didn’t, I wouldn’t care much if my crew neck showed. I’m at the point in my life where I’m good with looking decent, but don’t care much for what’s “fashionable.” If I look like my grandpa in the 1950s (my dad’s fashion sense was more 60s/70s), so be it.