WMUTeach - thank you for the recommendation on the chalk pen - will have to order one and then hide the YELLOW one so that i dont ever use it on the top fabric 🥺 the yellow is useful for other things, but obviously not in this scenario!
After using the Magic Eraser, your suggestion of water & microfiber cloth, baby wipes, and a Shout Color Catcher i have gotten most of the yellow chalk out. Who knows whether it was one thing or a combination of all i used - its gone and thats all i care about! I really had to work on it.
Thank you for all of your help!