Colorization - what was it's purpose?

[Jorge_Stolfi]

1. The person who drew those illustrations knew what those plants were and drew them for their own personal use.  But that begs the question, if they knew those plants, why was there a need to add color?

Indeed, if that was the case, why draw the plants at all?
 
Apart from the colors, the use of vellum (poor as it is) and the illustrations (poor as they are) strongly suggest that the VMS was created to others, not for personal use by the Author.  

It could have been for a specific person, or he may have hoped to sell it eventually.  Or maybe it was meant to be his legacy to humanity, a repository of his knowledge that he did not want to die with him.  Or maybe it was meant for shared use by the Secret Mystic Society of Women Who Bathed With Their Hats On.  But I think this last alternative is rather unlikely.

"Made for others" is not totally certain only because I recall some eccentric American whose hobby was to "forge" ancient manuscripts, just for fun.

But again, I'm art impaired.  I'm still trying to comprehend why someone paid $181.2 million for paint splatter.

For the same reason that people paid tens of thousands of dollars for an NFTs, or for stuffed Beanie Babies bear...

All the best, --stolfi