Why Text Colour plays a major role in site visibility

It’s my third week of GSoC and I’ve been working on automatically creating CSS files for automated theme generator. While creating different background colours some text colours were more visible than others. After some search I came to know it’s being caused by contrast ratio .

The following image has a contrast ratio of 1.07 so it’s hard to read.

Greater ratio means greater visibility a minimum ratio of 4.5:1 is required because it compensates for the loss in contrast sensitivity usually experienced by users with vision loss and ratios greater than 7:1 is great for users with colour blindness or low visibility. So as I am coming to an end for creating Automated colour backgrounds, I’ll focus on keeping texts with high contrast ratio and also work on creating test cases.