Like has been stated it is an OEM version designed to cut costs(the less used an accessory or part is, the more expensive it tends to be since its not bought in bulk), if it was an ES board then it might not even be red and black and newer BIOSes might not work correctly on it, but I think you are okay. I would say as long as a normal BIOS flash works then you are fine(if a BIOS flash works then chances are its a final product, as I have some ES motherboards that dont work past very early dev BIOSes). I would keep it because that isn't a bad price.
Also its very hard to counterfeit a motherboard, I mean most who know the business somewhat understand that PCB manufacturers hold a crap load of power over motherboard vendors and do leak their designs(parts of their design, like how many power phases, what features they are using, and other stuff) to their competitors, that is why you might see certain companies seem to "copy" each-other, they are just finding out what the other does and mimicking it because they are succeeding with it (wait till a new gen like 9 series releases and you will see what I mean, there must be a reason MSI leaked so early and broke NDA so blatantly because they are trying to get the public to perceive something). Someone should create a PCB maker in the US where if they leaked stuff they would be demolished by a lawsuit in a fairly short period of time, however it can be a two way street, every company wants to know what their competitors are up too. The big companies might want to make sure they didn't leave something out or they are making sure everything is okay with their product, but smaller companies might really need to catch up because they were given design specs for a platform later than the bigger ones. Also PCB designs can be used to reverse engineer a product as well, and that is why those bare PCBs that some overclockers get as gifts, are usually of boards that have already hit EOL(end of line). It is possible that a PCB vendor sent a bunch of PCBs to a 3rd party who then soldered the right parts on and who wasn't hired by asus to do so(ECS and Pegatron being ASUS's trusted partners), however it is almost like counterfeiting money, the tools(machines) needed to do the counterfeiting is pretty damn expensive I don't see how one would pay for the machines with the profit from selling those boards haha.
I am sure its just an OEM, but always interesting to find motherboards that look different than retail.