Hi Glass,
You are right, there is nothing on record about the presence of coated diamonds in the core samples. I listed this in the bullet points as it had been suggested as a possibility on this board and elsewhere. It has been suggested that these coloured outer surfaces may have been a residual part of the hematite coating left by the caustic, but is yet to be proved.
According to Allan, the colour intensity rating was added for the purpose of describing those diamonds that were uncoloured inside with a coloured outer part. I have been using the word clear to describe colourless. This may be where the confusion arises and I apologise for that. Other than that, I do not remember Allan mentioning to be about there being a coating on the diamonds, just a coloured exterior.
Anyway, I hope that this helps.
peterjr