You likely wont find any horses described as a brown buckskin.. Sooty buckskin will be lucky.
Dark buckskin, maybe.
Most people are incredibly incorrect with their descriptions of their horses color. I've seen TONS of chestnut with white (FLAXEN) manes and tails labeled as palomino. Or Bay roans called BLUE roans (blue roan = black horse with roan --- bay horse with roan = bay roan!). Besides the thousands of descriptive terms people use... buttermilk, dun, grulla, tovero - its impossible to read through most peoples description