I got my info from Alf Stalsberg's site. He collected all three types. He is a well respected aquarist and has many years of experience with these fish.
http://www.lem.net/alf/aeq.htm
Scientific names for all animals are determined by the first specimen collected. Günther described Chromis rivulatus in 1859. The type (first) specimen was collected in the Rio Esmeraldas in Ecuador.
The fish we now know as the Green Terror in the US is from the Rio Guayas in Ecuador and the Rio Tumbes in Northern Peru. The same rivers the Red Terror is collected for the pet trade.
This fish is separated from the true "A" rivulatus from the Rio Esmeraldas by some minor anatomical features including size and coloration.
The fish Jeff has is the original Green Terror from Southern Peru imported back in the 70's for the pet trade. This fish is only found in Peru.
The confusion stems from people believing this fish was the "real" rivulatus. It's not. To make matters worse, the Rio Guayas "rivulatus is found with silver, red and orange edge populations.
There have been other kinds of rivulatus like fish brought in from Columbia too.
The blue acara was thought to be one species. Now it has been split up into at least five species and the scientific name "A" pulcher is now restricted to a fish found in the island of Trinidad.
You brought up the "Port" Acara. There are 12 "Port" Acaras now.
Sven O Kullander from the Department of Vertebrate Zoology Swedish Museum of Natural History has been working on the classification of South American cichlids for several years.
It is believed all the Green Terrors and Blue Acaras will be placed in a separate genus together.