There is a recent development of a variant of the Pterophyllum scalare species known as the “Bulgarian Green Angelfish” which is known for its unique green coloration. It is indeed a relatively new addition to the aquarium hobby, appearing only in recent years and it is considered a rare and in short supply. It is characterized by its platinum body with a green hue over the scales, with emerald green dorsal and anal fins. They are also known as “Bulgarian Seal Point” Angelfish in some circles, it is not yet a standardized common name and may be known by different name. As you pointed out, it is a newly developed strain and its rarity and popularity, make them more sought after among enthusiasts.