I would do a little research first, look to see what colors they offer and see if those match up to the options available. its possible they mis packaged two different types of stained wood. I.e.. Cherry, and dark cherry or two different woods. If the wood is different there cann be slight differences in finished staining if the wood grains are not from the same block. Or it could be they just gave you one of two different stained options.
Thats deffinatly a big difference in the appearance from one side to the other. I would be returning those. Wood is easy to sand out and refinish in small pieces. but as far as gun grips and stocks, i have come across the largest problem with refinishing wood for firearms. When you sand out all the current clear and stytain you end up taking too much of the actual material away, and this ultimatly ends up making the pieces too cmall to fit back properly.
Why dont you just find a local wood worker and have a set made. Small pieces like this are verry easy and fairly cheap to make.
Another +1 for ching's