Abstract: A glass composition which is essentially free of lead and cadmium includes 30 to 70 wt % SiO.sub.2, 1 to 25 wt % B.sub.2 O.sub.3, 0 to 10 wt % Al.sub.2 O.sub.3, 0 to 5 wt % Bi.sub.2 O.sub.3, 0.1 to 30 wt % CoO, 0.1 to 20 wt % ZnO, 1 to 30 wt % total of at least one of Li.sub.2 O, Na.sub.2 O or K.sub.2 O, up to 10 wt % ZrO.sub.2 and other optional ingredients. The glass composition can be used as a blue colored on-glaze enamel which relies upon the presence of Co.sup.2+ in a network-forming position in the glass to produce the blue color, with oxygen donors such as ZnO.sub.2, alkaline earth oxides and alkali oxides increasing the amount of cobalt occupying network-forming positions, and ZrO.sub.2 to provide chemical durability.