What colour is original Delft Blue pottery?

Original Delft Blue pottery is known for its cobalt blue decoration painted on a white glazed surface. The blue colour comes from cobalt oxide, a mineral pigment used in ceramics for centuries. Before firing, the paint appears grey or black on the pottery, the bright blue shade develops inside the kiln after firing at high temperatures. Early Delftware makers copied the appearance of Chinese blue-and-white porcelain imported into Europe during the 1600s. Some antique Delftware pieces used extra colours such as green, yellow or red, though blue remained the most famous style. Historians believe cobalt pigments reached Europe through trade routes from Persia and Asia. The white background came from a tin glaze applied over earthenware clay and some collectors often prefer darker cobalt shades found on 17th-century Delft Blue pieces.