People used constellations to tell the difference in the colors. Constellations were also used to group stars. Different places in the world may have different constellations, but today astronomy has a fixed set of 88 constellations. This set is based on the Greek set and later some southern constellations were added, for example Antlia - the air pump. Most constellations have names that come from Greek mythology, like Orion or Andromeda.