There is only one species, and it's called Theobroma Cocoa. There are "varieties" though, and those varieties are primarily "Criollo" and "Forastero". There has been a lot of talk about a "Trinitario" variety, but I think these days claims of it existing are somewhat nebulous at best.
Typically Forastero pods are smooth and shaped like a footbal with rounded ends, while Criollo has a rough exterior, sometimes distinct ridges in the shell, and a fairly pronounced pointy tip. Color is a bit all over the board, but Criollo is often a very pale green(but can also be yellow), while Forastero is usually yellow or red when ripe.
Like I said though.... Color is less of an indicator than the shape and texture of the pods.
Hope that helps.