I certainly agree that Paintshop Pro is better value for money than Adobe’s products, but you can get 30 day try-outs of Photoshop 7.0 and Photoshop Elements 2.0 from the Adobe website. However, they are big files and if you haven’t got high speed internet (DSL, Cable, etc.) then it will take a loooooong time to download. PS7 is the full-bells-and-whistles version, while PS Elements is a more basic version that still should allow you to do everything that you want to do. PS Elements has been very reasonably priced of late; you can currently get it for about $50 after rebates on Amazon, and for about $70 after rebates at Best Buy - although i don’t trust rebates too much - and a few weeks ago it was even cheaper.
One thing you might want to do if you’re going to be comparing colors with a view to actually changing your home’s decor is calibrate your monitor so that the colors you see on the screen are as close as possible to what you will see when you remodel your kitchen. You can find a tutorial on monitor calibration here; it’s actually not too difficult to do, especially if you have Photoshop, which has a Gamma setting that allows easier calibration. Virtually every digital photography site on the web says that monitor calibration is essential, not optional, if you want realistic and consistent color reproduction. It was the first thing i did after buying my digital camera. After all, there’s not much point finding a color combination that looks great on the screen, only to find out too late that it looks terrible in real life.