In following pairs, the one in which both transition metal ions are...

$d$-block elements form coloured ions due to presence of unpaired electrons in them. since there are no unpaired electrons in ${Sc}^{3 +}$ and ${Zn}^{2 +}$ ions, they are colourless.

No of unpaired ${e}^{-}$

${Ti}^{3 +} - [ Ar ] 3{d}^{1}, {Cu}^{2 +} - [ Ar ] 3{d}^{9}$

${Sc}^{3 +} - [ Ar ] 3{d}^{0}, {Zn}^{2 +} - [ Ar ] 3{d}^{10}$

$T{i}^{4 +} - [ Ar ] 3{d}^{0}{V}^{2 +} - [ Ar ] 3{d}^{3},$

No d-d transitions in ions with ${d}^{0}$ & ${d}^{10}$ configuration. Therefore they are colourless.