"Blue Dot Clusters" in Herbal Illustrations

[Sam G]

I think this phenomenon should be looked at from a wider perspective. If you flick through the large-plant images, you see that blue is used a lot in certain smaller plant parts. Seeing how often blue is used, I am almost certain that it is not literally blue but perhaps some catch-all shade for "dark color bit" or "bit that turns dark when dried".

They don't use black in the plant drawings, and brown is reserved for woody parts and some leaves. Hence, I think that the color is relevant but shouldn't be taken at face value.

Definitely.  I just like to rule out the possibility that the colors are intended to represent the actual colors of the plant if possible.  Both the blue and red in the herbal sections seem to have some kind of symbolic function, at least in some cases.