Why the transition metal compounds of Mn(II) are almost colourless?
Electronic configuration of Mg2+: [Ar] 3d5
The complexes with d5 configuration of Mn are centrosymmetric (having center of symmetry) and therefore d-d transition in these complexes is not allowed. The colour of the complex which is due to d-d transition is thus not present in Mn2+ compounds. Hence, they are almost colourless.