If you could make mutations on the genes of the peppered moth to decrease their selective pressure (make them blend in more), what changes would you make?

The Endocrine System.

What is the Endocrine System?
The endocrine system is made up of glands that produce and secrete hormones, chemical substances produced in the body that regulate the activity of cells or organs. These hormones regulate the body's growth, metabolism (the physical and chemical processes of the body), and sexual development and function. The hormones are released into the bloodstream and may affect one or several organs throughout the body.