There is no facility for any custom styling of words in the Rich Text area. We have to repurpose Bold, Italics, or now the Superscript/Subscript stylings in order to allow clients to do red alert text styling, yellow highlighted styling, etc.
I'd like to see the addition of 3 SPAN types in a Rich Text Area, which you can default to yellow-highlight, blue-highlight, violet-highlight. We'd be able to restyle these, of course, to whatever is needed for that client, e.g. Red text for a COVID policy alert message.