Surface lights automatically emit the color of the surface (so if you make a red texture emit light, it will be red light). You can also make light entities. I believe you use "color" "r g b" to set the color, the rgb values range from 0.0 to 1.0. "Style" makes lights flash - there are a few selections to choose from. I don't recall offhand, but I'm sure searching around on google will git you the answers you need. Be careful when using styled lights because:
a) It can be annoying to have blinking lights everywhere.
b) Each time the light on a surface changes, the engine has to re-upload the lightmap to the graphics card, which can cause a big framerate hit.
c) There's a hard coded limit to the number of different light styles that can be on a single surface.
