Coloured Text on Oregons

Mapsource/basecamp and older gps devices generally render text colours and sizes set in your TYP file using custom colours.

Unfortunately, Oregons and a few other gps devices apparently do not respond to such settings, with a few exceptions:

I’ve found text tagged with polygons does show up in different colours and sizes ; in fact if the font option for a particular polygon has not be set the text won’t appear at all!
Also, highway refs respond to font settings.

Has any one found a way of overriding oregons text size options?