question about the bloom found on skin of grapes

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What exactly is the bloom - does it refer to the waxy layer of oleanolic acid or does it refer to the microflora of organisms that live on this layer?

Why is it grey ? Is it the natural color of oleanolic acid or does it appear grey because of the numerous and uncountable microorganisms resident there?

Thanks folks

 

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Mind if i bump this up a bit?