Why does the blue paint look like this?

[ReneZ]

Hello Koen, yes indeed, that should be the cuprite. There might be more of this in the 2009 documentary.

I have no idea what has caused the pale yellow. Possibly an attempt to make a colour mix as mentioned above, or else something that 'went off' over time.
The azurite crystals look very bright for their 600 years, but that is something that I would have expected.