What is this inground pool wall actually made up of (gray, blue, white)

In another thread, I was advised to acid wash my pool walls to remove what appears to be crystalline calcium deposits - but - I stopped after doing only one section because of finding no plaster in a 10 year old in- ground pool.

Do you know what my pool walls are made out of?

Washing with a pressure washer & with muriatic acid, I find three perplexing layers ...

1) Sandy white crystals that bubble in HCl (most likely calcium)
2) Blue thin layer (maybe copper coating or maybe paint?)
3) Gray smooth stuff (probably plaster?) The gunnite must be below the gray smooth stuff ... right?

Here are a bunch of pictures. If you own a pool and you have an idea what happens to a pool in ten years use, maybe you can let me know what I'm actually looking at.

This is whitish crystalline sandy stuff coating the entire pool:

Here's a picture of that white sandy stuff on the pool walls: Here's the strange blue stuff on top of the smooth gray stuff: Here's the spa, coated with the blue stuff which is extremely thin: And, lastly, here's the gray stuff underneath all that blue stuff: What am I looking at?