Easiest way to explain Spalding, Indian, and Green. Indian is a species. The color and pattern mutations are varieties. Green peafowl are another species. The different kinds of Green peafowl are subspecies of Greens. A Spalding is a hybrid not a crossbreed. Hybrid is the mixing of two species like a horse and donkey making a mule. While a Quarter Horse and Appaloosa is a crossbreed since those are two breeds of horses.
A variety can be color or pattern. A Indian Blue Black Shoulder is a variety of the Indian peafowl. A Purple peafowl is a variety of the Indian Peafowl. A Spalding Split to White is a variety of Spalding peafowl.
White, White Eyed, Pied, and Silver Pied are caused by a gene called Leucism. It's the lack of pigmentation in the plumage/coat. A White tiger is not an albino tiger because it still has pigmentation in the eyes and skin. White peafowl still have pigmentation in their eyes and skin. That's why they are not an Albino. To be an Albino there has to be no pigmentation in the eyes, skin, plumage/coat. Leucism will always show up with another color or it will cover up another color depending on how strong the gene is. That's why when we say it can be split to White, White Eyed, Silver Pied, or Pied it's because it shows some white but not all of it. The other colors when we say split to one of the colors will not show at all until you see the offspring.
You also have Sex Link genes. Making it so one sex will have the gene or it won't have the gene while the other sex will only have that gene, carry it, or not have it at all. I'm not entirely confident with explaining the rest of the Sex link genes since I don't have experience with them so I will let someone else do it.