What's the evidence that the colors were added later?

[Jorge_Stolfi]

rainbows are connected to water and rain, right?

Well, yeah, but I have never seen any suggestion that water would pour out from the ends of a rainbow.  Rainbows often end on the ground, and anyone who has seen that would know that there is no water running inside tehm.

The only rainbow lore I know is that there is supposed to be  a pot of gold where it ends.  Which is a joke to catch fools, because by their nature one cannot ever get to the place where it ends.

It can be both. Look at the top of f82v. Here rainbow/tube is painted with red and yellow and connected to clouds. And water is falling from it.

Hm, yeah, I don't know how to make of that drawing.   Clouds and a rainbow could be an interpretation, but, again, why is water pouring out of the rainbow?

And why is the cloud packed so tightly against the rainbow, and only on one side?  Could that instead be a small pond held by an You are not allowed to view links. Register or Login to view.?

Anyway, if that is supposed to be a rainbow, I think is further evidence that the paint was not applied as the Author intended. He would have demanded a least a few more colors...

All the best, --stolfi