How long does it take for pimple scars to go away?

Depends: If true scarring has occurred, they may never disappear. However with excellent healing they are typically not very conspicuous. In the meantime do not pick and keep wounds clean.

Tincture of time: Most of the dark marks and red spots left when pimples go away are not scars, they are just marks. They go away by themselves, although they sometimes take their sweet time about it. True scars - depressions in the skin - are permanent, although dermatologists and plastic surgeons have a variety of techniques for making them less obvious.