Cobalt is a cool, desaturated blue, historically made using cobalt salts (cobalt is an elemental metal). The blue seen on many glassware is cobalt blue.
Color Coordinates
Hex triplet = #0047AB
RGB (r, g, b) = (0, 71, 171)
CMYK (c, m, y, k) = (100, 80, 1, 0)
HSV (h, s, v) = (210, 100, 67)