You may not even need this to be official. Could just introduce a custom theme for your own use using a browser extension like stylish. I say may since I don't

You may not even need this to be official. Could just introduce a custom theme for your own use using a browser extension like stylish. I say may since I don't know that would work for mobile or native apps, or maybe you're having to look at other people's computers through screen sharing or whatever. I don't know what to tell you in that case.