1. For homoleptic octahedral complexes, the color absorbed corresponds to the crystal field splitting energy $\Delta_o$:

$\Delta_o = h\nu = \frac{hc}{\lambda}$

So, larger $\Delta_o$ means smaller absorbed wavelength $\lambda$.

2. The ligand strength is directly related to the magnitude of $\Delta_o$:

• stronger ligand $\Rightarrow$ larger $\Delta_o$
• weaker ligand $\Rightarrow$ smaller $\Delta_o$

3. Given absorbed wavelengths:

• $L_1$ absorbs green
• $L_2$ absorbs blue
• $L_3$ absorbs red

In the visible region, wavelength order is:

$\lambda_{\text{red}} > \lambda_{\text{green}} > \lambda_{\text{blue}}$

Therefore, energy order is opposite:

$E_{\text{red}} < E_{\text{green}} < E_{\text{blue}}$

Hence,

$\Delta_o(L_3) < \Delta_o(L_1) < \Delta_o(L_2)$

4. Since ligand strength increases with $\Delta_o$, the increasing order of ligand strength is:

$L_3 < L_1 < L_2$

5. Checking options:

• A: $L_3 < L_1 < L_2$ ✔
• B: $L_3 < L_2 < L_1$ ✘
• C: $L_1 < L_2 < L_3$ ✘
• D: $L_2 < L_1 < L_3$ ✘

Therefore, the correct option is A.