Explanation

(b)
Colour of transition metal ion salt is due to $d - d\$transition of unpaired electrons of $d\$-orbital. Metal ion salt having similar number of unpaired electrons in $d$-orbitals shows similar colour in aqueous medium.
In ${VOCl}_{2}$ vanadium is present as $V^{4 +}$ and in ${CuCl}_{2}$ , copper is present as ${Cu}^{2 +}$.
So, _{23}V=$1s^{2},\ 2s^{2}\ 2p^{6},3s^{2}\ 3p^{6}3d^{3},4s^{2}$
$V^{4 +} = 1s^{2},\ 2s^{2}2p^{6},3s^{2}\ 3p^{6}\ 3d^{1}$
$3d^{1}$
[table] $\upharpoonleft$ | | | | [/table]
Number of unpaired electrons =1
and _{29}Cu =$1s^{2},2s^{2}\ 2p^{6},3s^{2}\ 3p^{6}\ 3d^{10},4s^{1}$
$\ \ \ \ \ \ \ \ {Cu}^{2 +} = 1s^{2},2s^{2}2p^{6},3s^{2}\ 3p^{6}\ 3d^{9}$
$3d^{9}$
[table] ⥮ | ⥮ | ⥮ | ⥮ | $\upharpoonleft$ [/table]
Number of unpaired electron =1
Hence, $VOCI_{2}\$and$\ CuCI_{2}$ show similar colour.