On the other day, screen on my Mac was looking rather ugly and whatever images I look at, they look very odd. Looked into several options including display settings etc., was almost decided to reinstall OS X. Reached out to Apple customer care and their agent tried investigating for about 2 hours including a remote session.
Then I started thinking what all I have done since morning; I remember changing size of mouse pointer, increased the contrast. While increasing contrast under Accessibility options, there is one option where user can increase contrast of display! That’s what causing to display images etc., in a odd way!
Lesson learnt is to remember the configuration to troubleshoot other problems!