Pair of mixed Angelfish?

[Sarjo Pepper]

I'm thinking about a tank for the future, with the possibility of having angels. So far my research has told me that the least risky scenario is to get a single angel and to keep it with peaceful non-nippers. Otherwise I have to worry about the possibility of pairs forming and becoming aggressive at spawn time. I also know that simply keeping two angels won't necessarily lead to a pair.
If I were to keep two different varieties, hypothetically a gold and a koi, would they be aggressive as they are not the same variety, and do they have the possibility of forming a pair even if they are not the same variety?

 

[Delapool]

Really need an expert. I have a pair with the female probably a third of the size of the male and very different colour. They have marked out a space of say a square foot but I've still got a fair bit of room left.

 

[HUKIT]

They're the same species just different color morphs so yes they can and will pair producing fry. As far as aggression that's more a individual personality and differs from fish to fish.