The top sheet isn't different. My shop fucked up mounting my first ones (with brown bases), and fucked up another pair (brown bases), and went somewhere else and bought 'em with red bases, but the top sheet was all the same.
generally, companies buy the same amount of two colors of base material. my silencers for example have a white base with black logos. since all the skis made this way would use much more white than black material, the design is inverted halfway through production so all the base material is used equally.