The way Maxis would handle it, assuming there is a limited number of these strings, they would just write every individual string and use the one that is appropriate. The main use of tokens is to extend translators capabilities. "{M0.xyz}" means that the text will be used when the Sim "0" is an "M" (Male), so you can put anything you want as "xyz". Implementing that for a few colors isn't really worth doing.
Once you put text into an STBL file, you can't read that text anymore, you are required to use the identifier for that text. This means that you can't swap any tokens before they get sent, because you can't even read the text anymore, you just have an identifier for it. That is unless you create a binary reader for the STBL files and manually identify what text is what (oof).
If you're going to put text within Python scripts, this problem doesn't even exist. When strings are made in Python, you can make them in any way you like, but then they become untranslatable by others outside that want to use STBL files.
If you're just going to swap individual words, it's better to just do what I explained at the beginning.
