Though the salts of s - and p - block elements are colourless, why are the salts of transition elements coloured?

Explanation

In case of s - and p - block elements, the ions can have s-p, p-d transitions. These transitions require energy as high as UV radiations, which are not possible through visible light.
Hence, s - and p - block elements generally form colourless salts. In case of transition metal ions, the `(n-1)d` orbitals contain unpaired electrons, which undergo `d-d` transition by absorbing light of a specific wavelength from the visible spectrum. Therefore, the salt appears to be of a colour complementary to that of the absorbed light.