The Voynich Ninja

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"The situation is much more complex than just an overenthusiastic blue painter:

• there is also too much white (blank)
  
• frequent, seemingly intentional combination of blue and blank elements
  
• there is too much yellow in the stems, a color notably lacking from the flowers
  
• calyxes in other manuscripts are green as a rule. While almost every large-plant page has green available to it (for the leaves), a disproportionate amount of other colors is preferred for calyxes."
  

After reading this post, I wondered if perhaps the blue flowers in the manuscript might have actually appeared green to the drawer. This might not have made a lot of sense, but according to a google search "what do color blind people see blue as": 

"People with blue-yellow color blindness (You are not allowed to view links. Register or Login to view./You are not allowed to view links. Register or Login to view.) generally see blue as green, light blue as grey, or find that blues appear much darker and less vibrant. While rare, this type of deficiency specifically makes it difficult to differentiate blue from green and yellow from violet or pink." 

Could this explain why they thought they were including pink when they were using a yellow pigment, or a green ink when it was actually blue?

It doesn't quite add up though. What we are missing in flower petals is yellow and pink/red. Instead, we have much more blue. With the condition you describe, the implication would be that the painter thought they were using green instead of blue, which still doesn't make sense for the petals.

Moreover, leaves are usually done in good greens. So I assume that this person knew pretty well what green looked like.

Or they are just faded. For example, if green was a mixture of stable blue and unstable yellow. A spectroscopy of paints would help.

I have a very mild (mildest degree) color vision deficiency. from what i know, colorblind people usually mix up red and green. Blue and green would indicate Tritanopia which is a very severe form of colorblindness. Not as severe as Achromatopsia but still relatively severe on the color blindness spectrum. I am not fully blind, and I only struggle with nuanced colors, for example black paint mixed with very tiny color amounts still looks black to me. I failed Ishihara test. I can distinguish bright saturated colors very well. A blue leaf would appear green, but a yellow petal still looks yellowish, not blue. Yellow and purple/pink could be confused but not blue with yellow. Red and blue appear distinct for Tritanopia, even though the blue is muted, it still red vs greyish blue which is pretty distinct. Tritanopia would not contribute to the deficiency of red. The "sunflower crop" still looks yellowish, and this won't explain the deficiency of red in VM.