Answer:Cr3+ and V2+
Step-by-step explanation:
Cd and Hg belong to group 12 which is sometimes referred to as post transition elements. They possess a filled d subshell (d10). Remember that the colour of transition elements is attributed to the presence of partially filled d orbitals leading to transition between the three degenerate lower energy t2g orbitals and two higher energy degenerate eg orbitals. If the element has a d10 configuration, such transition is impossible, hence its ions will be colourless.