Tropaeolum majus, better known as Nasturtium have a wide variety of colours. Gleaming Mahogany from Mr Fothergill's Seeds is one of my favourites. As you can see in the photo they grow well in pots. They are also good companion plants.
Another reason I grow these gems is because ants don't like them much. With my sandy loam, ants can be a problem. I also plan to use the photo as reference in a drawing.