metamerism

1:  isomerism especially of chemical compounds of the same type

2:  the condition of having or the stage of evolutionary development characterized by a body made up of metamers that is usually held to be an essential prelude to the differentiation of the more highly organized animals (as arthropods and vertebrates) through the disproportionate development and elaboration of some segments together with the coalescence, reduction, or loss of others

3:  the phenomenon exhibited by pairs of color metamers the problem of metamerism in matching artificial with natural teeth