Novel environmentally friendly inorganic blue pigments based on amorphous tungsten oxyphosphate, (W(1-x)Ln(x))OP2O7-delta (0.10 <= x <= 0.29; Ln = La, Eu, Gd, Y, and Lu) were successfully synthesized, and their color properties were characterized. Among the samples, (W0.76Eu0.24)OP2O7-delta shows the most brilliant blue color. The b* value corresponding to blue chromaticity of the(W0.76Eu0.24)OP2O7-delta pigment was -25.2, which exceeds that of a commercially available iron hexacyanoferrate pigment (Prussian blue, b* = -15.6). Since the present (W0.76Eu0.24)OP2O7-delta pigment consists of only nontoxic and safe elements, it could be an effective alternative to conventional blue pigment.