Was the paint added later? And is the artist also the scribe?

[Jorge_Stolfi]

However, in 11r we do not see the kind of bleeding that appears in 65r and 65v.

Actually, looking closely, I see some cases of that bleeding on You are not allowed to view links. Register or Login to view. too.  Check (B) in the 
image below.

   

But I still think that it does not necessarily imply that the ink was wet when the paint was applied.

A surface intended for ink writing ideally should strike a balance between water-loving (wettable, hydrophilic) and water-repelling (non-wettable, hydrophobic).   

It should be hydrophilic enough to hold any ink that is applied to it.   Otherwise the ink will bead up and not form a trace.  Like what happens when you try to use water-based paint on plastic.

But the surface should be hydrophobic enough to prevent the ink from spreading beyond the place where it was applied.  Like what happens if you try to use water-based paint on wet paper.  This spreading is often desired in watercolor painting, but hated in most other contexts.

On page f112r, the Scribe apparently ran into a spot on the vellum where the surface was too hydrophilic, and as a result his Ch became blurred (A).  He then tried to stay away from that bad area in the following lines, but kept running into it (B,C).
   
The last step in the manufacture of vellum/parchment was to apply some light coatings to the surface and smooth it with a pumice stone (a "natural sandpaper").  I don't know exactly which coatings were used, but of course they were such that the surface became good enough for writing -- not too hydrophilic and not too hydrophobic.

But once the surface was coated in ink, even dry ink, that balance could change.  For instance, a common ingredient in ink formulas was gum arabic, which is mostly a carbohydrate between sugar and starch.  It stays dry in normal air, but it remains water-soluble and presumably water-loving. 

In those examples you posted, the big green stain inside the leaf looks like it was a very wet puddle.  Gravity would try to spread it out, but the vellum surface apparently was not hydrophilic enough to let it do so.  But, as you noted, it found it easy to travel along the ink traces, for quite a distance.

So the question is whether it could have done that over dry ink, or whether the ink had to be wet.  I am undecided...  

Anyway, note that those ink traces are [censored]. Compare them to the [censored] traces, for example on the last leafstalk that branches off the stem on the right side.  Thus, even if the ink had to be wet for the paint to run along it, that would show only that the green paint was applied at the same time as those specific traces were [censored].

All the best, --stolfi