# Explain: the compounds of copper (II) are colored but those of zinc are colorless?

You have a ${d}^{9}$ electronic configuration in the case of $C u \left(+ I I\right)$..
...and you gots a ${d}^{10}$ electronic configuration in the case of $Z n \left(+ I I\right)$.. $C u \left(+ I I\right)$ has a ${d}^{9}$ electronic configuration, and the colours exhibited by transition metal complexes are in part due to $d - d$ transitions (i.e. the energy difference in orbital configuration corresponds to the visible region). These electronic transitions are not available to the $Z n \left(+ I I\right)$ complex, whose $\text{d-orbitals}$ are completely filled.