Here's a link:
https://medlineplus.gov/druginfo/meds/a601124.html
Along with a lot of other helpful information, it says changes in skin color are one of the known side effects.
Why are you using a steroid ointment for a rash, do you think it's psoriasis? If you think the rash has a bacterial cause, you might want to use Neosporin or Polysporin or some other over-the-counter antibacterial ointment, not a steroid. Steroids in ointment form can do things to the skin that aren't what you would like to have happen.