After my stye went away i still had a bump, googled it & found out it is a chalazion but now my eyelid is way darker than the other. why? treatment?

May fade with time: A chalazion is basically a 'blocked up' oil gland on the eyelid that results in inflammation and swelling. They are almost never infected. They usually resolve with frequent warm compresses but sometimes the residual material remains as a small bump. I have not come across eyelid darkening after resolution of a chalazion, but i imagine it is possible. It will likely fade with time.

Skin pigmentation: Changes can be part of healing. A stye and a chalazion are inflammatory lesions. This can cause the pigment cells in the skin to increase pigment, resulting in increased pigmentation of the skin. For instance, it is common for folks with mild to moderate pigmentation (asians, hispanics, middle eastern heritage etc.) to have increased pigmentation at healed sites of skin injury.