Add color customization for TalkerLog in TalkerScreen

[Rodsevich]

Is your feature request related to a problem? Please describe.
If you create a custom log (suppose a metric/setting/etc) you must attain to the default grey color because of limitations on the enums Talker uses.

Describe the solution you'd like
I'd love you can define another property in the TalkerLog for enforcing the color for those logs.

Describe alternatives you've considered
I have no way of tweaking the behavior as a user, the only alternative was to forfeit the color I need.

Additional context
Enums can't be extended, but sealed classes can. Taking in consideration that enums will never be extended and custom logs are a thing needed, why can't we change to classes approach instead of enums?

[Mooyeee]

This was actually something I was thinking about too, I may play around a bit when I get some time since it would be very useful.