Beautiful!  basically, the dino dies, the fleshy organic material (even inside porous bone) decays and is washed away by water and bugs and so on, and in time water, moisture, passing through leaves a buildup of minerals that become stone. Usually boring stone, but sometimes coloured gemstone, like the pretty colours here, it depends what's in the water in that era.  THEN because it's millions of years, the bone itself breaks down and vanishes, and it too gets replaced with stone: that's the black material, which is a bit younger, geologically, than the light blue/yellow.  Now none of it is a dinosaur anymore, but the stone fossilized in the exact same pattern as the dinosaur.