When translating Theophilus' blue color 'Lazur' the main stress has always been laid on azurite. However, it must be pointed out that there were two other possibilities, namely genuine ultramarine or a white pigment colored with a blue vegetable dye. The author has, on basis of actual paintings from the period, arrived at the result that 'Lazur' in the early Middle Ages in Northern Europe was genuine ultramarine from lapis lazuli, but he does not, however, exclude the possibility that other pigments have been used as substitutes. In Theophilus' chapter 1/15, the one dealing with wall-painting, it is indicated that the parts which are to be painted with 'Lazur' have to be underpainted with a grey colour. This technique is only of importance if the pigment is used for glazing and it is genuine ultramarine.