some white-on-black color improvements for drracket

please include on the release branch
fix cons/c use in contract

related to PR 14222

This doesn't completely fix that PR because the
implementation says that bytes are allowed and
the docs don't allow that. My guess is that the
implementation is wrong, not the docs, btu I'm not
sure and this may be a backwards compatibility
kind of thing, too. Also, path->collects-relative
should probably be considered (it doesn't allow
bytes? as an argument).