Conflict Solver: Update diff view colors when changing the view mode/layout

When solving merge conflicts, it would be very useful if the diff view updated its colors when you change the view mode at the top (left+merge, all, right+merge, etc). So that you can see the diff visualization correctly.

For example, I get this in 3-way mode:

When changing to the left+merge mode, most of the green should go away, as those 2 files are nearly identical. Currently the colors are unchanged, which makes it difficult to view the diff, since it's colored "wrong" compared to normal diff views.