>
>What you refer to is "Verdaccio"
>
> Verdaccio - an Italian name for the mixture of
>mars black and yellow ochre and very small
>amounts of white and red resulting in an olive
>tone, brownish soft green. Verdaccio also refers
>to an under-painting done using verdaccio color.
>During the Renaissance, verdaccio became an
>integral part of fresco painting. This color is
>used for defining tonal values, creating
>complete monochromatic under-paintings.
>Architectural details in frescoes are often left
>in verdaccio without any additional color
>layers. Michelangelo’s Sistine Chapel is the
>best example where you can clearly see verdaccio
>under-painting left as is on most of the
>architectural details of the composition.
>

I seen on your Facebook page for the IDAL Event, that you have a 4-photo sample of this. The first one on the bottom left, is that the Verdaccio before the color overlays on the second one to the right of this first photo? It makes sense to me this way...