well first of all, the brown part of the eye, its called the iris and its not always brown as it can be blue for example, in persons with blue eyes.
A white spot (is it a spot what you are referring to?) on top of a brown iris, would have to be located on the cornea, a little round glass shield or lens that covers the iris. So when you think there is something on top of your brown/black/blue iris, it is actually on the cornea and most probably its a scar from a trauma. It could also be a corneal ulcer, which are usually painful, and are caused usually by microbes (bacteria, fungus in people who had a trauma with for example a tree branch or leaf, or even parasites, in persons who clean their contact lenses with tap water).
If it happens to be a scar it will stay there forever as the cornea cannot heal to a transparent tissue again. It can heal ok, but it loses its optical properties. If its an ulcer its an urgent condition.
A white spot on the cornea its called a leukoma or leucoma and it can be caused from anything from trauma (like we just covered it) to cancer (retinoblastoma) or caracts, including some genetic conditions or caratcs related to aging.
There is also sometimes an "invasion" of the white tissue of the eye into the cornea, but this is a very bad explanation for a process called pinguecula or pterygeon. (I answered a question here about pinguecula, look it up, maybe that is what you are referring to).
no its something your born with
Walter Elias Disney had light brown eyes.
dark brown
Sally Rides eyes are a light green or light brown.
Baby Bash has brown eyes.
Justin's eyes are dark brown.
Tyga has light brown eyes
His eyes are light brown.
Her eyes are light brown.
brown.....
Her eyes are either hazel or light brown
What people dont know is that theres different variations of hazel. you have dark hazel eyes. people with more green than brown are light hazel and people with an equal color of green and brown r medium hazel.