I bought the game from GOG.com. Installed it. Installed the latest version of killdap's restoration mod, which included the high-res mod. Ran game. Perfect audio, no picture at all.
I extract the high-res files into the main Fallout folder. I then uninstall the high-res mod. I run game on Admin privileges. Perfect audio, picture looks inside out. Can't discern what the main looks like because it's too busy looking like confetti. I exit game.
I google solutions and try out all of them (I'm pretty sure) in this (Fallout 2 Colors Problem) thread. The last try was clean installing, installing the restoration mod, and then sfall. I do the ini file thing.
Now, I get a error about not being able to load cities. I google that. I follow instructions. I run game again. It loads, but still no picture. I uninstall the high-res mod and the same color confetti greets me at the main menu.
I'm frustrated beyond all belief. I have directx 11 and I'm on Windows 7. For some odd reason the game won't let me run it on compatibility mode. I have an older machine (IBM ThinkCentre M50 series), but a Pentium 4, 2 CPU 3.00 GHZ, 4GB of Ram isn't that bad, right?
I've been searching and googling, but it's like a whole week later. Somehow, I feel that what finally works will be something stupid I've overlooked or missed. :-/

Not sure if this will help you or not or if it's even related to your problem but i had a issue with fallout 1 (not tried FO2 yet) not showing colours correctly, i fixed it by deleting the DDraw.dll file from the game directory then i patched the game with the High Res patch, loaded the game up and switched on 16bit colour in the SCR options menu and then restarted the game.

For everyone who may still be having trouble with color problems or display problems with black screens, etc., check out this link. Randomnly found it in a topic on gamefaqs and it helped fix any display issues for me. If it doesn't work the first time then restart your computer and try again, it worked for me when the tool randomnly didn't work sometimes (probably just my computer).
http://blog.macuyiko.com/2009/07/solving-color-problem-red-grass-purple.html