You can display any HTML as a message. To do this, select the message type " Show as is" in the field settings.
<text style="background: black; color: white"> The white message on the black backgroud</text> |
Or hex colors
<text style="background: #000000; color: #FFFFFF"> The white message on the black backgroud</text> |
Colors: https://htmlcolorcodes.com/