The breeders who named them red turquoise did not use the criteria you propose. The red refers to the amount of red color in the base of the discus. Let me explain!
In nature, a discus with full red base is very rare. A discus with a full blue pattern and full red base is even more rare. This was the dream! But most wilds with a nice full "royal blue" pattern, do not come with solid red base color. More often, there is a large range of colors which include red elements, but also composed of brown tones, golden tones and grey tones. This is quite a variable feature of the wild discus. But what the breeders wanted, the dream, was a full red base color, and a full pattern. This did not come easily, and took many years to refine and perfect, to the stage where the breeder could assert with some authority, that they bred true. A true pinnacle of breeding ability with discus. It matters not how much blue there is, or even what pattern the secondary blue color takes, just the fact that the discus has a full red base, imo, makes it worthy of the name red turquoise.
Rod