If they are both males, once they settle in one will probably bully the other as he'll have decided the tank is all his.
Two females may coexist peacefully but there is still the possibility of conflict.
One of each could result in a dead female. These fish need to choose their own mates and a random male and random female from the store tank won't necessarily get on.
Watch them over the next few weeks and their behaviour towards each other will tell you if you need to separate them or if they get on together.