a compound made in the first part of an experiment,

Question

[Co(NH3)5Cl]Cl2 appeared to be a dark brown/orange/purple color.

This product was then used as a reactant to synthesize [Co(NH3)5ONO], which was a red color.

how do you account for the differences in color between these two?

Answer 1

See

http://en.wikipedia.org/wiki/Jahn-Teller_effect