Careful consideration for the undertone's VALUE and INTENSITY aids in efficient painting in the field.
Since I believe that a landscape painting without atmospheric perspective just isn't a landscape, I am always finding ways to promote it in my paintings.
Five devices for promoting atmospheric perspective:
• Cool it.
• Grey it.
• De-emphasize detail
• De-emphasize contrast
• Lighten it.
Undertone Value and Contrast Control
It's "de-emphasize contrasts" that I pay a lot of attention to. In short, I control my foreground, middle ground and background contrasts from the very start. If my undertone is getting in the way of that, I'm not working efficiently. I want to avoid having to go back into the painting to lower the contrasts in the background. The value of the undertone should work for us and not against us here.
The other aspect of the undertone is intensity or color saturation. I build my paintings on relationships, so if my initial tone is too saturated, I have less control over it from the start. It can inhibit my ability to judge subsequent masses as they are blocked in. Too colorful an undertone, and I am always competing with it. Too grey, and I can't seem to make the block-in colorful enough.
Finally, I think the undertone color (hue) is up to the artist. Whatever conveys your inspiration and sentiment the best.