I saw a request for a mod like this in the 'Mod Request' section of the forums so I got bored and made it in about an hour. Nothing too pretty here, just 16 different colored bricks. I didn't put much effort into the textures either so take that into account before criticising.
The way to make the bricks is 1 brick and 1 dye on the top row of your crafting table (shapeless recipes coming soon Now you too can have shapeless recipes!).
I built the mod against Forge 1180, but it should work all the way down to 1.7.2.