I always use terracota pots prefering hem to the glazed coloured one.

I would choose a pot in a Terracotta shade for that particular plant too..your choice of 'proper' Terracotta,or plastic..whichever you prefer..

A big terracotta with a pale, chalky, blue-green wash painted on? Might age nicely?

I have some nice sandy coloured salt glazed pots and one nice rich deep brown one. though as a contrast to orange the colour wheel suggests blue/purple. but it is such a personal taste I'd not want to suggest a colour.

Very dark green?

Thanks all. Food for thought. I'me putting another question on re potting on.