Which of the following statement(s) is/are correct?

Permanganate ion, pertechnate ion and perrhenate ion are all dark purple coloured species

In both haemoglobin and oxyhaemoglobin, iron is in +2 oxidation state

Both $\left[Ni{\left(CO\right)}_4\right]$ and ${\left[NiC{l}_4\right]}^{2-}$ are tetrahedral complexes

Chromium form highly oxidizing compounds in +6 oxidation state, whereas the equivalent compounds of molybdenum and tungsten are not appreciably oxidizing