Showing coloured pony... advice please

Sorry if I've posted this in the wrong area.

I have a lovely 13.2 lightweight Welsh cob x Arab mare. Her passport states she is dun and white but her 'dun' bits go very dark in summer.

Everywhere I take her I get comments about how well she'd do in the show ring and although showings never been my thing I'd like to give it a go.

Other that the coloured classes, what other classes could I show her in? Baring in mind I'm an older rider on a pony also!
Also would it be better to show her plaited or as a native?

I'll try and post a picture.