Check My Colours is a free-to-use web application for analyzing the color contrasts used on a web page.
It checks the foreground and background color combinations of all DOM elements and lets us to know if they have enough contrast when viewed by someone having color deficits.
Once a URL is submitted, it lists all the elements + their contrast levels and marks any problematic elements. Also, it allows us to play with their colors online to find the right color.
P.S. The tests ran are based on the algorithms suggested by W3C