Tooltip Background Color

How can I change that tooltip background of warcraft 3 from gray (default) to black or another color ?

IIRC, tehre is a texture that it is just exactly that. Browse on the GUi directory from a folder, and you might find it.

You have to change it in the game interface.
In your editor go to Advanced -> Game Interface
Check the box: Use Custom Game Interface (at the top)
They are in the Image section, not even a quarter the way down the list. You can import custom images for each part if you find one you like.
Hope this helped.
+Rep? (Thanks in advance)

Thanks but somebody already told me about it.

you can use player color textures for this, they located somewhere isn war3.mpq