C = Carbon
H = Hydrogen
O = Oxygen
N = Nitrogen
P = Phosphorus
S = Sulfur
Fe = Iron

The CPK Color Scheme

CPK = Corey, Pauling, Kultin. This color scheme was used in early physical models of molecules.

The CPK color scheme used in this tutorial follows that used in RasMol with the exception of Fe (which is green in RasMol's CPK scheme).