Here are some additional comments provided by Phil Plait. I have a special page on my web site that talks all about star colors. Hot stars are bluer, while cooler stars are red. A red dwarf is a tiny red star, pretty much like the Sun but much cooler and smaller. They are very small, about the size of the Earth.
Brown dwarfs are a newly discovered type of object, which are midway between stars and planets.
They are too small to be real stars, but too big to be called planets.