RTV Colors

Just a quicky about RTV sealants. I searched and read that Copper was recomended in a few places because its rated at a higher temp. Another thread said that color doesn't matter much as long as you use some. Well, I'm rebuilding my engine and I'd like to know which color to use where? Can I use copper everywhere, or are different RTV's for different applications. For instance, do I need a different color for the water pump since it seals water, not oil? And for the intake what color?