I have explained this many times in these forums as well...my last description is:
False GT is a misnomer. You should think of GT as 3 different fish which are all referred to as green terror:
Gold Saum
Silver (or White) Saum
Silber Saum
The Silber Saum (which is the rarest in the trade currently) is what should be referred to as the original green terror. The other two would be what you refer to as the false GT, especially the gold saum as it is the most common in the trade currently. There was a time when they thought all three were the same species of fish.
The main difference between the silver and gold saum is the coloring on their fins. The Silber Saum resembles a silver saum but the scales would appear inverted compared to the other two. This means that the gold and silver saums have scales that appear as dark with a light outline while the silber saum has scales that are light with a dark outline.