Which ion is coloured Cu⁺ or Cu²⁺ ?

Cu in neutral state Z = 29

1S² 2S²2P⁶3S²3P⁶4S²3d⁹ which rearranges as 1S² 2S²2P⁶3S²3P⁶4S¹3d¹⁰

Cu⁺  1S² 2S²2P⁶3S²3P⁶4S⁰ 3d¹⁰

Cu²⁺ is 1S² 2S²2P⁶3S²3P⁶4S⁰ 3d⁹

Cu ²⁺ is coloured since d-d transition takes place in Cu²⁺ which has 3d⁹ in its electronic  configuration  whereas Cu⁺ has completely filled d orbital where such a transition is not possible.