Comment 3 for bug 280041

If you have an inspiration you can try to find more suitable colors and change the code directly.
You need to change RGB values in the lib/diffview.py file, around 43 lines you should see following code:

colors = {
    'delete': (QtGui.QColor(255, 160, 180), QtGui.QColor(200, 60, 90)),
    'insert': (QtGui.QColor(180, 255, 180), QtGui.QColor(80, 210, 80)),
    'replace': (QtGui.QColor(206, 226, 250), QtGui.QColor(90, 130, 180)),
    'blank': (QtGui.QColor(240, 240, 240), QtGui.QColor(171, 171, 171)),
}

QtGui.QColor there are defined R,G,B values to mark different kind of changes. E.g. delete -- currently drawn in red, insert -- in green, replace -- in blue. Second value used to highlight interline changes (currently it's darker color). You can change these values and run qdiff again to see effect.

When you'll be happy with new colors, please attach a patch to this bug report.