Try using carbonated water.
Try the easy method first with warm water and a bit of dish liquid on a cloth and gently blot.
Hi Wanda: I use warm water and just a bit of Dawn mixed in. If that doesn't work, then put a bit of Clorox in and use a tooth brush on the stain. Good luck
Call the company that installed them, or go to Home Depot or Lowes and talk to sale staff in the blind department for suggestions. Good luck !