Iv got windows 7.
Fallout 2 btw

Right click on the Fallout 2 executable in Windows Explorer and select the 'Compatibility' tab. Check off:

[/] Run this program in compatibility mode for (Windows XP SP3)
[/] Run in 256 colours
[/] Run in 640x480

Apply... Ok.

Use Killap's unofficial patch or the Restoration Project 2.2. Mod (which includes the patch).

Unofficial patch 1.02.28 (released July 21, 2013)
http://www.killap.net/fallout2/patches/unofficialFO2patch.exe

Fallout 2 Restoration Project 2.2 (released July 21, 2013)
http://www.killap.net/fallout2/expansion/2.2/F2_Restoration_Project_2.2.exe

Don't install the patch after you decided to use the Restoration Project Mod, because it will strip all the new content.

I cant find a compatibility tab

Are you looking on file exporer or in the game explorer?
The game explorer not show the properties. You need to open in the windows explorer the location in that you instaled the game, find the fallout2.exe file, right click it and select the compatibility tab.

Elsewhere I'm not have the color glich bug with the gog version.

Patch the game, the GOG version doesn't provide all bug fixes. Fallout has a strong community which put a lot off effort in fixing all issues the developers left over and there were lots.

Even the GOG team suggests using unofficial patches, see this thread: http://www.gog.com/forum/fallout_series/fallout_2_mods