$Ti^{3+} = [Ar]\, 3d^1$ (one unpaired electron)
$Fe^{3+} = [Ar] \,3d^5$ (five unpaired electrons)
$Co^{2+} = [Ar]\, 3d^7$ (three unpaired electrons)
So all of them are coloured.
(આપેલ : પરમાણુક્રમાંક $\mathrm{Sc}=21, \mathrm{Ti}_{\mathrm{i}}=22, \mathrm{~V}=23, \mathrm{Cr}=24, \mathrm{Mn}=25$ અને $\mathrm{Zn}=30$ )