Which complex absorbs the wavelength of red light?

The molar ionic conductance of the octahedral complexes:
$(i)$ $PtCl_4 \cdot 5 NH_3$ $(ii)$ $PtCl_4 \cdot 4 NH_3$ $(iii)$ $PtCl_4 \cdot 3 NH_3$ $(iv)$ $PtCl_4 \cdot 2 NH_3$
Follow the order:

Select the option containing the correct order of the given parameter.

Calculate the overall complex dissociation equilibrium constant for the $Cu(NH_3)_4^{2+}$ ion,given that $\beta_4$ for this complex is $2.1 \times 10^{13}$.

Which is the incorrect observation?

What is the color of a cobalt chloride solution?