In Gvim, run :hi Green guibg=green.

Afterwards run :hi Green to display the highlighted color. Note, that this is a
rather dark green than a light green, that is expected from the X11 color
names. So apparently, the W3C Colornames are used. Gvim uses the function
gdk_color_parse() to parse the colorname into a color definition. I have
verified using a debugger, that this function returns the wrong color. It
should return 0x00FF00 but instead does 0x008000 which happens to be the W3C
Green definition.

If this is the wrong package to report against, please assign to the correct
package.  Thanks.

(Side note, Athena gvim works correctly).

This has been discussed on the vim ML, starting here:
http://thread.gmane.org/gmane.editors.vim/118330