This here is a guide I made to be able to use roblox colors in decals or clothing. I find it would work best for those that are modelling and need a decal of the same color paint. Here's the guide: http://www.roblox.com/Roblox-colors-paint-program-guide-item?id=94470061
Hope this helps. Read the description!
just print the screen of the colour chart in studio and use the x tool to get the exact hue of the colour... or go to wiki.roblox.com and search for the brick colour hues.