Panchlora nivea, by the look of it? The dark brown individuals are nymphs (i.e. immature cockroaches).
I'm not aware of any problems with mixing cockroach species except the some species will hybridise (Blaberus spp. - Death's Heads - are notorious for it).
Yes, definitely Panchlora (the ones in captivity are generally labelled P. nivea, but I don't know if they really are this species or one of the other genus member;- identification below genus often isn't too reliable in captive invertebrates.)
Some of the omnivorous cockroachers with carnivorous tendencies are willing to take a bite of slower relatives. However, most frequently kept cockroachers, incl. green, are essentially plant eaters with slight omnivorous tendencies and can generally be mixed without major problems.
