Soulfish pretty much summed it up but I can go into further detail. warning the following is pretty boring.
Red zebras are probably my favourite fish because of what I am about to explain. the estheraes were named after Esther Grant, wife of Stuart Grant one of the exporters from Lake Malawi (Kambiri Point,Salima)
Red Zebra, aka Metriaclima Estherae is caught from Minos Reef, central eastern Lake Malawi. Males are blue, there are white ones too but they are rare. Females are orange. There are also orange blotch females. About 10km south of Minos reef you get yellower females, further still down near Chiofu you get brown females.
All Estherae have yellow "egg spots" on the back of their dorsal fin. This is the only species of metriaclima (formerly pseudotropheus) that has egg dummies in a spot other than the anal fin.
There is a COBALT blue zebra also at Minos Reef with brown females, (metriaclima zebra blue reef) this fish does NOT have egg dummies on it's dorsal. So - the metriaclima estheraes know to stay away from Blue Reefs ( and not crossbreed).
ok. about breeding.
Blue Male + Orange Female = Blue male fry, orange female fry.
Blue male + OB Female = Blue male fry, OB female fry.
WHITE male + O female = ORANGE male, orange female
blue male + brown female = blue male, brown female
so those fish you see in the hobby "red zebra" are probably metriaclima estherae IF there is a blue male and they have egg dummies on their dorsal. However most common in the petstore is "RedxRed" which was created if you remember above I said white male + orange female = orange males and female fry.... what the florida guys do is import a white male and breed it like crazy
If you guys dont see any egg dummies on your redxred fish they are either a) not estherae, b) not red zebra or c) a crossbreed.
References -
Diving experience at Minos Reef, Chiloleo, Gome and Chiofu, where I watched breeding occur in the wild
Ad Konings, in conversation
Personal experiences in the aquarium however my white male has not bred AFAIK
Lake Malawi Cichlids 3rd Edition. Ad konings does a very good jon of explaining the different fish at Minos Reef - red zebras etc.... what I wrote above was trying to paraphrase what he has in his book