Update 2020: This post is now outdated and archived, but feel free to read it to remember what it was like. ?
This is also useful for sites which have a limited selection of colors and support color codes. Here’s a preview:
See? The color code is located near the top-right. What you have to do is to add a number (#) sign before it.
Why not try it? It’s easy, simple, and nice. You can even add it to iGoogle.