Base Color Green Technique

I've never realized the importance of underpainting till now. Thank you so much to Master Jose Tolentino Jimenez for giving me these idea to try underpainting using green as base color. 

So I made some research via the internet and found quite some good articles and how to's. So it was a classical technique called verdaccio or the dead painting. 

Employing this style ables me to identify tonal value.