Why Hydrogen Peroxide is Kept in Dark Plastic Bottles?

The chemical structure of hydrogen peroxide is shown below:

Due to the Oxygen-Oxygen link, Hydrogen peroxide breaks down slowly at room temperature, but quickly in presence of heat, certain catalysts (e.g., metal ions), and light.

2 H2O2 → 2 H2O + O2

Brown-colored containers limit the wavelengths of light that can be absorbed by the solution, restricting the initiation of the disproportionate reaction.