I'm not certain how much the painter tried to actually mix yellow and blue (violas are often yellow and blue) as opposed to trying to shade them into each other, because the painter appears to be aware that they don't mix well (in the sense of creating a new color), aware that the chemicals tend to stay separate from one another.
The green pigments appear to blend better and the painter took advantage of this and created quite a range of greens in the VMS, by mixing a base green with other colors, but as can be seen by Koen's examples, mixing the base blue with the base amber does not really result in green in the same way as one would expect with modern pigments.
I can't remember what McCrone had to say about the green (maybe they were uncertain about it), but from looking through the manuscript, it appears to be a more cooperative pigment than the blue.
The green pigments appear to blend better and the painter took advantage of this and created quite a range of greens in the VMS, by mixing a base green with other colors, but as can be seen by Koen's examples, mixing the base blue with the base amber does not really result in green in the same way as one would expect with modern pigments.
I can't remember what McCrone had to say about the green (maybe they were uncertain about it), but from looking through the manuscript, it appears to be a more cooperative pigment than the blue.