Please make diff colors configurable

[DanielGibson]

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Being red-green colorblind, git gui's diff view is hard to parse for me. Right now I'm patching git gui to replace #00a000 with blue, but each time git gets updated, I have to reapply the patch..

It would be nice if the colors could just be an configurable in the options menu, like in gitk.
Or maybe the color.diff.* settings of git config could be used.

Either way, it would be very helpful for colorblind people (that in many countries make up 8-10% of the male population!), if the diff colors would be configurable