I agree, sashes come in many colors, And the style and color can also represent ones, house, lineage etc.
I'm a member of the fan group KAG short for Klingon Assault Group, And we do conventions etc in costume.
I just finished a sash in black leather. Really they can be almost anything you want. We use this approach,
" if it looks Klingon it can be klingon ". If you would like to see photos. I have them at a site called Klingon Space as do many members there!
I would support this as long as it didn't change the default colors, since they don't seem to be colors available in the ordinary spectrum.
That should not be a problem since the commbadges already have a different range of colours compared to the regular uniforms.
So something similar for the sashes would certainly make things interesting.
After looking at the available ones again I must say the ones I'd be interested in wearing because of their shape (simple yet elegant) have an unappealing rather "wooden" colour tone while the ones with an intersting silver-greyish tone look too much like something from the circus.