Comment 4 for bug 37603

My guess would be that the titlebar text is fine because it has a dark shadow which enhances the contrast. The progressbar text which is white on orange might be difficult to see for some.

I'm not sure if this represents a valid test, but I played with it a bit in gimp, first making it grayscale and then fading out the contrast a bit. See attached file. We do of course have the high contrast theme, but that may be overkill for those who are 'just' colour blind.