The Andorians are blue-skinned humanoids from the planet Andor in the Epsilon Indii system: along with Humans and the Vulcans, they were founders of the Federation; the Aenar introduced in the final series of Star Trek: Enterprise are a closely-related sub-species.
As well as blue skin they have white hair and a pair of long antennae on their head. The Andorians were first seen in the original TV series but only with their return in Star Trek: Enterprise have we seen an Andorian female. They now have much improved makeup including neat animatronic antennae that actually move.