Which one of the transition metal ions is coloured in aqueous solution?

Valence shell electron configuration of ${\mathrm{Cu}}^{+}$ is ${\left[\mathrm{Ar}\right]}^{18}3{\mathrm{d}}^{10}$; so n = 0

Valence shell electron configuration of ${\mathrm{Zn}}^{2+}$ is ${\left[\mathrm{Ar}\right]}^{18}3{\mathrm{d}}^{10}$; so n = 0

Valence shell electron configuration of ${\mathrm{Sc}}^{3+}$ is ${\left[\mathrm{Ar}\right]}^{18}3{\mathrm{d}}^0$; so n = 0

Valence shell electron configuration of ${\mathrm{V}}^{4+}$ is ${\left[\mathrm{Ar}\right]}^{18}3{\mathrm{d}}^1$; so n = 1

As ${\mathrm{V}}^{4+}$ has one unpaired electron and so in presence of water as ligand it will undergo d-d transition of electron. Hence ${\mathrm{V}}^{4+}$ ions will produce colour in the solution.