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

Valence shell electron configuration of Cu+ is Ar183d10; so n = 0Valence shell electron configuration of Zn2+ is Ar183d10; so n = 0Valence shell electron configuration of Sc3+ is Ar183d0; so n = 0Valence shell electron configuration of V4+ is Ar183d1; so n = 1As V4+ has one unpaired electron and so in presence of water as ligand it will undergo d-d transition of electron. Hence V4+ ions will produce colour in the solution.