I want some explanation for my eyes changing colour?

Many reasons : Changes in pigment, freckles , blood or blood vessels. Corneal scars or swelling. All sorts of stuff. Probably more concerning if the eyes are different colors from one another versus both changing slowly.

Few possibilities: The color of eyes are mostly associated with iris color pigmentation and sometimes scarring or deposits in the corneas (such as cholesterol). Changes in color over short time periods are much more likely just from more reflections off of the room lighting or other ambient light conditions. Some hazel, green, or blue eyes can do this more than darker colors. Hope that helps!