The orange colour of K2Cr2O7 and purple colour of KMnO4 is due to:

Concept: Origin of colour in transition metal compounds

$d \rightarrow d$ transitions require partially filled d orbitals.

Charge transfer transitions occur when an electron is transferred between ligand and metal orbitals — these give intense colours even with $d^0$ or $d^{10}$ metals.

$\text{K}_2\text{Cr}_2\text{O}_7$: Cr is in +6 state → $3d^0$ (no d electrons)

• Cannot show $d \rightarrow d$ transition
• Orange colour due to charge transfer (O → Cr) ✓

$\text{KMnO}_4$: Mn is in +7 state → $3d^0$ (no d electrons)

• Cannot show $d \rightarrow d$ transition
• Purple colour due to charge transfer (O → Mn) ✓

Both compounds have $d^0$ metal centres — their intense colours arise exclusively from charge transfer transitions.

Answer: Option (1) — Charge transfer transition in both