Ok, I'll try and help clear this up a bit:

For Blue scroll/Essence: Its possible to get them at all times. (Think of them like in any seal scroll treasure and you randomly get a 1 star ninja)

For Purple Scroll/Essence: You get them guaranteed with a 10 pull (within 10 pulls since the last). Which one you get is based on RNG. It will be one or the other.

For Gold Scroll/Essence: It's possible to get at 50-60 Pull. Following the purple pattern, its completely RNG. It will be one or the other.

For Red Scroll: This is independent of everything else. From what I have seen, it can be between 190-240 pulls. I know for a fact it is independent because it took me 240 pulls. I did a 10 pull and got both my Red R2 Resistance scroll (lucky me!) and a Gold Scroll (bleh) at the same time.

Personally I have probably gotten one gold essence and the rest scrolls. I don't think you were asking about how many points it takes to get them, so I will leave that alone....as it should be straightforward.