Make new comments stand out more.

In this comment, Eliezer asked for a change to make new comments stand out more: http://lesswrong.com/lw/h8d/ritual_report_schelling_day/8tuu

This is a cheap attempt to do that by using a brighter green.

This is also the first time I've ever tried to change something using Github, so my apologies if it does not work or if I am doing something obvious wrong here!