ui(board): label font color

Summary

I'm having the issues for group board (Self-hosted GitLab Enterprise Edition 11.10.4-ee). Sub-problem of #11021 (closed), ping @smcgivern.

Steps to reproduce

Have label with light background. Add that label to any issue via board sidebar, it will show up at lists with white font color that's hard to read. Workaround: refresh to get readable black font color for light backgrounds.

@smcgivern : Is this the same as https://gitlab.com/gitlab-org/gitlab-ce/issues/53174, but the other way around? 🤔

Yes. Furthermore, have issue on board list with light background (#FFECDB) and black font, but add unrelated label, also then it first label will swap it's font color to white again.