Is this appropriate?
If you feel it’s a bug (poor color choice) in a theme, maybe you should file it as one. You can get help with this at https://help.ubuntu.com/community/ReportingBugs
Whilst this is most likely a friendly-dig between colleagues/friends, I fear it could be read as one person trying to shame another into a change, which I believe is wrong, let alone not looking good with regards our community.
This is my opinion, and maybe I’m too close to be objective, but to me this site is the wrong place for bug-reports on theme color-choices (if that’s your point).