Color of the water on f79v as an indicator of religious cleanliness

[gerrydelasel]

My feeling is that we have "good water" - blue and "bad water" - green here. 

I came to the same thought when I first saw f79v, but on other pages it is less consistent, so I'm less inclined to read anything into it now. I tend to think an artist just colored things in depending on what color paint he happened to have mixed up. Run out of blue? I'll carry on with that green I mixed yesterday.