I think you might be out of luck unless you want to do the expensive custom bags mentioned earlier.

Cheap bags some in every color because they are cheap to produce.

Expensive bags come in shades of grey/black because grey goes with nearly all bike colors and the manufacturers focus on high volume sellers.

Occasionally you find one that comes in different accent colors like this one...
https://www.amazon.com/YVO-Handlebar...60-spons&psc=1

Usually the accents are red, blue, or green (from my non scientific observations) But everyone once in a while you'll see a purple or orange or something a little more fun. You may just have to be patient on the purple bag. There was one floating around Amazon last year that came in all colors. But it looks like it's gone.