I've had the same problems. Water is purple, grass is grainy, and teal is yellow while purple is blue (on the map that is).
I've got II without the expansion(s?) and both the "disable visual themes" method and the "open up screen resolution window" method have not worked...
I'd try the batch method, but seeing as this is a family computer, whenever I alt-tab out of AoE it is because somebody needs to check their email or similar and having to reboot explorer and close it again would just get annoying...
What other methods have I not tried that do not involve closing explorer?
Here is a method that does not need you to close IE or do anything other than move some files into the directory where the game is installed and create a new shortcut via right clicking on an exe and selecting "Send to --> Create Desktop Shortcut".
Oh and the game will start in a window... but once you start the actual map or mission it goes full screen (the menu is the only thing that is in window)
Readme is included. Here are some mirrors:
Mirror 1 - http://rapidshare.com/files/396032407/AOE2\_expFix.rar.html (will die after 60 days of no download)
Mirror 2 - http://www.megaupload.com/?d=T7B2SZL8 (will die after 6 months of no download)
Mirror 3 - http://www.mediafire.com/?tx5nmdwj2ym (will die after 6 months of no download)
enjoy.
PS - ive been using this for about 9 months now on Windows 7 64bit, AMD 5200+ (dual core) 4GB of ram and a Radeion 4850 video card.