First off please note: This suggestion may exist as I didn't know how to search for a reasonable name
Anyway, my suggestion is to add default colors to the color palette, like a named sub-section on the bottom. Like I myself would have the section named 'Minecraft Chat Colors' and set them to the reasonable HEX via the ACP.
You can change them permanently? I know you can do it per-font change.
And yes possibly that. Something like what Google Docs does.
Just change the custom to whatever you want in the ACP http://grab.by/mG7w