Ross, you didn't say whether you had the OEM pads put on (which Brent assumed was the case) or aftermarket pads.
I am no expert in brake pads, but I have replaced my back pads with aftermarket and bought pads for the front ot have ready when I'm ready to do them. (That's like saying "I'm not a doctor but I play one on TV").
First, nothing I have seen indicated any pad would not have a wear indicator. Maybe that's normal for some brand, but seems odd since the visual inspection of the pads starts with looking at the wear mark.
Second, they make pads out of different kinds of materials, but it's the pad itself which would have different coloration depending on the type of brand.
You can do a search at this site and learn a lot about brake pads...it helped me decide which type and brand to buy.
But the best thing would be to cruise past the dealer and ask. It may be that they didn't have a matched set in stock and gave you two brands...or two compositions. I would think that last option would be only a minor problem, since the stopping power of different composition pads might cause one rotor to grab before the other, but heck, the rear tire only has one rotor, so grabbing from one side of the wheel and not the other isn't automatically bad.
OK, someone else with more experience than me weigh in on this line of thought.