Chihuahuas can be any color or mixture or colors, but never merle (dapple).
Merle - Merle is not a purebred chihuahua. This is a solid base color with speckles of another color, commonly blue or red. Some merles have unusual lightly colored eyes which is due to the merle gene that affects the pigment. Merles are not purebred chihuahuas and can't be registered with the canine association. The merle gene ia a modified gene, it genetically ulters and lightens dark coloured coats, including the pigment in the eye. Merle chihuahuas can have hearing and sight problems due to the gene they carry.