$\begin{array}{*{20}{c}}
  \lambda &{{\lambda _1}}&{{\lambda _2}}&{{\lambda _3}}&{{\lambda _4}} \\ 
  {{\text{Absorbed}}}&{{\text{light}}\,\,{\text{Red}}}&{{\text{Green}}}&{{\text{Yellow}}}&{{\text{Blue}}} 
\end{array}$

Wavelength of absorbed light decreases.

$\therefore$ Increasing order of energy of wavelengths absorbed reflect greater extent of crystal fleld splitting, hence, higher field strength ot the ligand.

$Energy\; blue \left(L_{4}\right)>\operatorname{green}\left(L_{2}\right)>\operatorname{yellow}\left(L_{3}\right)>r e d\left(L_{1}\right)$

$\therefore \quad L_{4}>L_{2}>L_{3}>L_{1}$ in fleld strength of ligands.