General antonyms:
* Even
* Uniform
* Smooth
* Clear
* Unblemished
* Perfect
Antonyms specific to skin:
* Radiant
* Luminous
* Flawless
* Porcelain
* Complexioned
Antonyms related to color:
* Solid
* Consistent
* Unmarred
* Harmonious
The best antonym will depend on the specific situation and the meaning you want to convey.