It makes your hair lighter too, not just your horse's. It makes your skin darker because (if I remember correctly) the UV rays cause your body to produce more vitamin D, which creates more pigment cells in your skin. Hence, a tan!
It has been getting really hot and humid here so both my horses are shedding a lot now. The birds will have really warm nest this coming winter. It is really neat though because it is the opposite of last year. Last year I brushed out brown hairs to find black hair, this year I am brushing out black hair to find brown hair. I will have to take new pictures, but first I have to remember to charge my battery.
My mare is chestnut sabino; four white socks, blaze, and some roaning (not normal 'roan'...roaning associated with her being sabino)...she also has a few more bird catcher spots this spring...gotta get some new pics.