Abstract: Polymerizable compositions are described containing colored polymerization indicators which confer a visible color on the unpolymerized compositions. Upon polymerization, the compositions exhibit reduced or eliminated color. The compositions can also change their opacity during polymerization. The compositions provide easy visual differentiation between the unpolymerized compositions and substrates on which the compositions are placed. The compositions are useful in clinical and laboratory applications such as those involving teeth, dental implants, orthodontic materials, artificial teeth and bones.