Which of the following ions are coloured in solution?

V³⁺

V³⁺ is coloured in the solution because it contains unpaired electrons in (n-1)d shell which will help in d-d transition.

₃₀Zn : [Ar]4s²3d¹⁰   ;   Zn²⁺ : [Ar]3d¹⁰

₂₂Ti : [Ar]4s²3d²    ;    Ti⁴⁺ : [Ar]

₂₉Cu : [Ar]4s¹3d¹⁰  ;   Cu⁺ : [Ar]3d¹⁰

₂₃V : [Ar]4s²3d³     ;    V³⁺ : [Ar]3d²