How Do You Take Over Spray Of Mystic Tan Off?

You can't. Only time will remove a spray tan, so if it is done badly or with streaks or it's too dark, there's nothing you can do. If you got too much of a sunless tan, you can try exfoliating  with a brush, or use a cream with AHA's, but it should be gone in about a week on it's own.
Anyone considering airbrush tanning should let the salon or spa people know how much of a tan they want. Generally it's a good idea not to go too dark  with a mist-on tan or it looks unnatural. For best results,  use mositurizers beforehand for a week to smooth the skin. More information is at  Airbrush, Spray-On or Mist-On Tan