Why is whiskey brown? In general, whiskey is brown because it comes into contact with barrels. Alcohol is a solvent, so it leaches flavor and pigment compounds from the wood it’s aged in. The longer a whiskey spends in a barrel, the darker the color.
Notice I said “in general.” There’s also a big difference in color between whiskey categories due to the types of barrels used for aging, and whether or not caramel coloring is permitted as an additive.