A Lyme rash is called a erythema migrans or EM.Typically a red rash develops, that expands gradually and often clears in the center, so that a ring is formed. This is also called a bulls eye rash. But it doesn't always look the same: there may form multiple rings around one tick bite spot, there may not really form a ring, but just a red expanding rash, and the color may be more bluish-red. On dark skin it will also look different.