You say you have a white crayfish, which I'm assuming is the species P. clarkii (would need to see pictures to be sure). If the blue crayfish is the same species, then it might be okay to add it if you have at least 20 gallons of tank space.
If it's truly an "Asian" crayfish as they're advertising then it is NOT AT ALL safe to add it. North American crayfish (which is what your white crayfish most likely is) are NOT AT ALL safe to house with crayfish from other continents. North American crayfish (family Cambaridae) are carriers of a disease called the crayfish plague (or crayfish pestilence). Crayfish from other continents (families Astacidae and Parastacidae) are highly vulnerable to the crayfish pestilence while North American crays are immune.
If your store is selling a true "Asian" crayfish and you were to bring it home to your white crayfish, the blue "Asian" would more than likely die from the crayfish plague. If you can get some good pics of both crayfish (especially top looking down pictures), then we could make a better judgement.
