Why Facebook, Twitter and google using Blue Logo??

Question for Programmers

Why is Facebook Blue in Color

Facebook has gone through some major redesigns in the past few years but one part that has more or less stayed the same in all those years is the site’s blue color.
Everything is so blue about Facebook right from the sign-up page to the logo, their mobile app and even the site pop-ups that have shades of blue. Why?
A New Yorker story on Mark Zuckerberg explains why Facebook is all blue in color. It says the young Facebook founder is color blind but can see blue:

"Colors don’t matter much to Zuckerberg; a few years ago, he took an online test and realized that he was red-green color-blind. Blue is Facebook’s dominant color, because, as he said, “blue is the richest color for me – I can see all of blue.”

Answer..--->

i)Colors don’t matter much to Zuckerberg; a few years ago, he took an online test and realized that he was red-green color-blind. Blue is Facebook’s dominant color, because, as he said, “blue is the richest color for me – I can see all of blue.”
"There were a lot of different color iterations," Kedar says. "We ended up with the primary colors, but instead of having the pattern go in order, we put a secondary color on the L, which brought back the idea that Google doesn't follow the rules."
(from an interview with Ruth Kedar by WIRED writer Sonia Zjawinski)

ii)Blue colour doesnt strain your eyes, for example in any of your text documents turn background colour to blue and read the matter in it. and do the same with any other colours. you will feel the difference.