The slightly different shade is caused by browser applying gamma correction to colors in PNG, but not to any other colors.

To work around it:


Save image as sRGB with gamma 2.2 (that's the default in almost all programs, so if you don't have config options for it, you don't have to do anything).
Use image optimizer to strip gamma information from the file (that prevents browsers from trying to "correct" the file).


You'll find more information about cross-browser compatibility in PNG that works article.

How to export PNG to be compatible with all browsers
Most paradoxes involves self-reference, the only exception known to me is Yablo's paradox, however it is still debated if it is really without self-reference. So, I was wondering, are there other known paradoxes that works without self-reference? 
