Among ${\left[{\mathrm{TiF}}_6\right]}^{2-},{\left[{\mathrm{CoF}}_6\right]}^{3-},{\mathrm{Cu}}_2{\mathrm{Cl}}_2$ and ${\left[{\mathrm{NiCl}}_4\right]}^{2-}$the colourless species are

Given, Compounds
We need to find that which of the compound is colourless species

${\mathrm{TiF}}_6^{2-}$ and ${\mathrm{Cu}}_2{\mathrm{Cl}}_2$ are the species without colour. 
${\mathrm{Cu}}_2{\mathrm{Cl}}_2\text{ is }2\left(\mathrm{CuCl}\right)$, making it diamagnetic. Thus, it misses colour. 
Ti in ${\mathrm{TiF}}_6^{2-}$ contains no d electrons, hence there is no colour since there is no d-to-d
transition,

Therefore, the correct option is D