Do you like Google's Favicon from 2012? That blue one with little contrast? No?
Then use the old one from 2009 which is colorful and easy to identify.Want the old-school icon from 1998 instead?
Here you go: Google Favicon 1998For Google Chrome:Google Favicon 1998 - direct downloadGoogle Favicon 2009 - direct download
By someone else: G Favicon Fixer - chrome store
This add-on was made to be small, fast and efficient, it uses as few resources as possible.
This is why every icon has it's own version (and small icon :P). If you want to change other sites icons as well, see:Greasemonkey
(when you use it anyway)or any add-on dedicated to that job...