Make it easier to discern the message author if user colors match in small chats

### Your use case

#### What would you like to do?
Currently, in 1-to-1 chats or in small group chats it's hard to quickly tell apart message sources if the respective user name colors match. I'd like to be able to tell apart messages at a glance using user name color, so i think there should be a way to change it.

#### Why would you like to do it?
Picking out distinct colors in a chat is, i think, a lot easier and quicker than relying on the avatar picture or user name. It's especially annoying in 1-to-1 chats because then everything just blends together.

#### How would you like to achieve it?
I'd like to be able to set custom colors for individual users which i talk to most often. This would let me improve readability in chats where it matters most. I want to be able to select from the set of default colors that are already used in the theme for user names, there's no need for custom rgb codes. It's not a problem that the number of colors is limited because, imo, there would usually be only a few chats where color clashes happen regularly enough to be a bother (and i could set the same color for multiple people if they don't appear in any chats together).

### Have you considered any alternatives?

I guess chat bubbles would also solve this (i've seen some other issues proposing this) but custom user name colors seem like a feature that's a lot easier to implement and is less invasive. Also i don't like the bubbles because they waste too much space and custom colors would, imo, improve readability as much.

I'd also be fine with this somehow being solved automatically, e.g., don't assign matching colors in a chat if the number of users doesn't exceed the number of available default colors, but i guess that might not be possible if user name color consistency across chats is desired.

### Additional context

_No response_