CCTextMarkedColorer

CCTextMarkedColorer is a CCTextModifier that colors text characters in an alternative color if they are contained within special marker characters. Assign it to a CCText component to color its contents.

You can create one via Assets / Create / Text Box / Marked Colorer.

colored text inspector
marked colorer, making everything between '[' and ']' violet
If you want the markers to be invisible, use a font that doesn't include them so they won't be displayed.