Lobelia erinus

Today I bought five lobelia erinus for $10 (Aus). There were no labels on the pots, so I'm not sure what cultivar they are, but one was a bluey-purple and the others an intense ultramarine, my favourite colour. They are native to southern Africa and I am yet to find a photo on the internet that does justice to their colour. Here is a photo I took the other day of a neighbour's lobelia. 

This Wikipedia article describes the different shades of blue. The ultramarine originally used in painting was made from high quality ground lapis lazuli from Afghanistan. It was very expensive and artists usually needed wealthy patrons to buy it for them. The pigment was often used to colour the Virgin Mary's robes in paintings. The painting below, by Sassaferrato, appears in the National Gallery's Making Colour exhibition, which examines colour in art. 

Ipomoea purpurea, or Morning Glory is no doubt classed as a weed in Sydney, but the colour of the flowers is divine. 

Cobalt blue pots can make a nice contrast in the garden. Might try some deep orange nasturtiums and sapphire coloured lobelia trailing from a blue pot. The Empress of India nasturtium is a dark, rich orange. Here is a photo from the Diggers Club website: