Remove Yellow/Pink/Brown

I have the luscious theme and I bought the upgrade to customize color/font/ccs.

The banner (it’s a small yellow/pink/brown) image at the top of the page and below menu titles does not go with my color scheme at all. I have learned from other forums that is in an image and that it can be changed in CCS, but unfortunately am still clueless as to what to enter to change the image and where to put that information.

The site is: https://www.bethalexanderfitness.com

Thank you very much for any and all insights ??