Prism color colored pencil - light Cerulean Blue each Prism color colored pencil features a thick, soft core made from brilliant, light-resistant pigments, to ensure smooth, rich laydown and color saturation. The colors are easily blended, slow to wear, lightfast, break-resistant, and waterproof. Each pencil contains a 3.8 mm lead core that is enclosed in a round cedar casing that is lacquered to match the core.