The reason why facebook is blue is because the founder Mark Zuckerberg is red-green color-blind and blue is the richest colour for he can see. But if you hate the blue that facebook uses, then now you can replace the primary interface from blue with any colour that you like.
Colorbook extension for chrome browser is simple tool for changing the color theme on Facebook in just a click.
# Install Colorbook Extension : Link
After you install it, you will notice a Facebook icon on the address bar. Click it, and you will see a color palette pop-down.
Select your favourite color. I recommend using a soothing color close to cool colours which will help your eyes if you spend lot of time on facebook. You can also ask a friend with blue colour-blindness to use this extension so that he or she may see a better looking version of facebook.