Non Canon Dragon Colors for Pern.
I know that Ruth is strictly speaking the only non-standard dragon color ever to have existed according to the creator. However, I also know that, fandoms regularly mix in a slew of non standard dragon colors. Personally I'm totally fine with this. (not that anyone needs or has sought my approval).
To me though, it's fun to obey the rules or guidelines (at least a little) so for devising non-standard colors I've always kept in mind that Anne has stated multiple times that when she was figuring out the colors she just did G for girls and B for boys.
Thus we get Gold and Green for the females and Bronze, Brown and Blue for the males.
In keeping with that idea I would put forward non-standard colors in this way.
Additional Female Dragon Colors
Garnet/Gules-(both shades of red)
Grulla could also work...it's really pretty on horses.
Additional Male Dragon Colors