Color Developing Agent 1 (CD-1) is the first in the series of color developing agents used in developing color films. It is the organic compound N,N-diethyl-1,4-benzenediamine (DPD), which is usually in the form of the monohydrochloride salt.[1] In color development, after reducing a silveratom in a silver halidecrystal, the oxidized developing agent combines with a color coupler to form a color dyemolecule.