(a) Copper metal shows +1 oxidation state because its electronic configuration is $[\mathrm{Ar}] 3d^{10} 4s^1$. It can easily donate one electron from $4s^1$ and exhibit +1 oxidation state. (b) $\mathrm{V}^{3+}$ and $\mathrm{Mn}^{2+}$ are coloured transition metal because of presence of unpaired electron and shows $d-d$ transition. While $\mathrm{Sc}^{3+}$ and $\mathrm{Ti}^{4+}$ are colourless because here $d$-orbitals are empty and there is no $d-d$ transition take place.