One way to brighten up drab HAs is
Hearing Aid Safety Device to Cover, Protect, & Prevent Loss of Children's Hearing Aids!
Son currently has red ones that are a bit large for his Oticon Tegos & a flesh-tone w/ zebra stripes pair for Oticon Safaris that are a bit small for the Tegos. They were free, so that's tolerable.
We previously had a light blue pair that I gave to another poster.
They're very nice people to work with; if DS wants another color, I'd certainly buy from them again.
I've seen other pull-on covers in many colors, but they weren't quite what I was looking for at the time.
Stickers can be had at the stationers or other shops and you could change art as the mood strikes. Maybe some of those fancy diamantes and other things for fingernail art could work.
I think you could creatively turn "bland" into beautiful for you.