She is a silver dapple and the brown effect is due to the sunburnt ends. When silver dapples are out in the sunlight a lot, their hair turns to a mousy brown or light chocolate brown color and they usually maintain the dappling effect. I have a mare that is silver dapple and she does the same thing when left out in the sun. Another way to know between a gray and a silver dapple is that grays lighten with age while you silver dapple will generally darken or stay the same color no matter what age they are. Her mane and tail appear white but I would also guess if Stacieandtheboys looked really close at her tail it would have multiple colors mixed into it making it a flaxen tale and the mane may be the same way. If you were to body clip her completely the dapples would turn almost white/silvery white and her body would be a lighter silver color. This is a website that kind of explains the markings and what the silver gene does to coat colors, it is the first one that popped up so it is not the best I have read, but is works! Silver dapple gene - Wikipedia, the free encyclopedia
Yep, it is official, I am a silver dapple freak! Something about them I just love.