Winsor & Newton Cotman Water Colours are a range of water colours that are made to our normal high quality standards but costs are kept to an economical level by replacing some of the more costly pigments with less expensive alternatives. Each colour has good transparency, excellent tinting strength and good working properties. Prussian Blue is a deep blue colour. It was made by German chemist Diesbach around 1704 making it the first synthetic blue pigment. It quickly gained favour as an alternative to genuine Ultramarine.