Modify diff colors

[xiongtx]

Follow-up on #293.

• Make diff colors darker
• Have ediff-*, magit-diff-* inherit from diff-*

Note: the diff-changed-* colors have not been touched; I can't figure out a way to make the yellows fit the zenburn-yellow{-,+}*theme. It'd be great if someone wants to take a crack at that.

Highlighted (top, point in region) and unhighlighted (bottom):

3-way Ediff:

[bbatsov]

I can't figure out a way to make the yellows fit the zenburn-yellow{-,+}*theme

I don't quite get this. The existing 3 colors don't look good or what?

[xiongtx]

The contrast is pretty awful :man_shrugging:.

[bbatsov]

I guess you can use something like color-ligthen/darken to produce darker versions of the yellow (e.g. by steps of something like 10-20%). I'm not expert in colors myself, but this seems reasonable. Or we can use orange?

[impaktor]

Either way, looks to be an improvement. 👍

[xiongtx]

I guess you can use something like color-ligthen/darken to produce darker versions of the yellow

I think I've had enough mucking w/ :rainbow: for now :tired_face:. Let's get this merged and address the yellow later.

[impaktor]

@xiongtx what is it that should be yellow? Is it something derived from vim's zenburn, or the original diff colours? Screenshot?

[xiongtx]

The diff-changed-* faces should be a certain yellow. The default ones work well w/ the diff-added and diff-removed I've implemented here.

Don't have a screenshot handy. You can play around w/ scaling the Zenburn yellows if you like.