Using a toned canvas takes away the fear and indecision of painting for many artists. You already HAVE something on the canvas. Mostly when you’re painting, you’re using push-pull. That is, pushing the background into the back, and pulling the foreground up front. You see this more often with artists drawing on toned paper, such as, pastel artists. This is a very old technique, maybe centuries old.
I like it because it seems as if the tone color (whatever I may have chosen) fills in the broken spaces of my paintings. A search on the internet will turn up quite a few artists who use this technique.
Most of the time, I will take leftover paint at the end of a session and tone a bunch of canvases just to have them on hand. Although I do not use this technique all the time, it’s great to be able to grab a few canvases as I’m heading out for some plein air painting. I just seem to be able to get a head start on getting the basics down. However, you can do this on location with just rubbing in some local colors with a rag. It’s entirely up to you.
My preference is for warm colors or even some very dark colors but I have used many – burnt sienna, dark brown/grey, blues, greens and even purples (yuck). One artist I know, Caroline Jasper, uses red for her canvases which adds an element of sparkle, and Wyatt LeGrand uses some very dark tones which also works well for him.
If you haven’t tried this technique, just try it for a few times to see how you like it.