Chihuahuas are often referred to as being either "deer head" or "apple head," depending on their appearance and physical characteristics. It's a common assumption that deer head and apple head are official varieties of the Chihuahua. But if you read the breed standards for the Chihuahua, you won't find them listed as such.
Fawn is a color that is very common in Chihuahuas and has several varieties like a sable fawn, blue fawn, and fawn & white. Other colors and markings you can find in Chihuahua breeds are marked, splashed, merle, sable, brindle, Irish marked, piebald, tri-colored, bi-colored, speckled, flecked and ticked.
the term teacup chihuahua is mainly an american term. it’s often used to refer to the size of a chihuahua and shouldn’t be used to categorize a specific type of chihuahua as you would reference a short-haired vs a long-haired chihuahua or a deerhead chihuahua vs an applehead chihuahua.