Does anyone know how to set the background colour of just a section of text within a RichTextField on the Blackberry?

I already use the offsets, attributes and fonts arrays to make changes to the appearance of certain sections of the text, but I would like to add a highlight colour to the background of one section too.

I know there is a protected method called getBackgroundColors that returns an array of colors to be used, which I can overwrite. But I have tried this and that method never seems to get called in my code, I don't actually know how and when the underlying implementation of the RichTextField actually use this method. Any ideas?