- Original Response -
If you want to use colored text in lang files,
you can use "Formatting codes" with the prefix "&".
e.g. "&c" represent red.
Answer to the other question,
sorry about that language file changing is not in plan yet.
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- Edited Response -
As supplementary information,
Spigot (1.16+ as I know) now support using `§x` for RGB colored text.
As other formatting color, you can use prefix `&` (or just use `§` directly) in language files.
`§x§1§2§3§4§5§6` and `&x&1&2&3&4&5&6` represent HEX color `#123456`
More info and example:
https://github.com/jyhsu2000/BannerMaker/issues/23