Tyrrau a thoeau, Caernarfon (towers and roofs, Caernarfon) - Working in just two colours is possibly the most difficult use of colour because the colour of choice has to represent every tone between the lightest (the white of the paper) and the darkest. Shapes therefore have to be pared right down to their most basic whilst at the same time being as descriptive as possible. Where the colour represents two very different elements (in this instance where the sides of the towers are the same colour as the background hill), one largely depends on what the eye knows to be true. The landscape and sky were purposely left free of any black, so that the eye is drawn to the dark shadows of the castle and the roofscape of the town.