chat color--feature request

I realize this won't be a priority, but a nice addition would be the ability to change the chat theme color for each conversation like in FB messenger. Both users would be able to see the most recently set color

The issue names no files, tests, or entry points. Start by locating the chat conversation UI and how conversation metadata is synchronized between users; define the supported client platforms and the expected behavior for setting and displaying a per-conversation color before estimating the work.

Written by the indexing model from the issue text.