After many trials and attempts at making a textlabel have two separate colours with richtext, I have finally come here for support as nothing I’ve tried has worked.
I’m trying to use it inside of an overhead ui, expecting the output of "[+] Username".
I’ve had the same problem before, which I fixed by turning on RichText only after I’ve formatted the text. I think RichText does not keep up with changes to its text.
Try turning it off and setting it back to true after updating your text.