Blame mass production for your inevitably being faced by the often-intimidating, bright white ground of a new canvas. It's easier and cheaper to produce canvas primed in white, which artists can then color themselves, than to sell canvas primed in various colors. (Think about how many colors pastel paper comes in!) Unfortunately this means many people think that white is what you should start with, rather than it being only one option.
The Impressionists popularized painting on white, with dabs of broken color having an added luminosity from the white. They did experiment with grounds in other colors, such as neutral greys, but this tends to be forgotten.
The color and tone you choose for a ground obviously has an impact on the tones and colors you use in the painting, even more so if you're using transparent pigments. The more transparent the color, the less its chroma (saturation) on a colored ground than on white.
A dark ground means you could leave dark tones in the composition unpainted; similarly a white ground for light tones. A mid-tone ground means you need paint in the darks and lights, and makes it easier to judge how dark/light a tone is, the contrast between colors. On a white ground all colors except white will be darker than the ground.
"A toned ground can be used to create atmosphere or mood, to unify a composition, indicate lighting conditions, or to give sculptural form to an object by giving depth to shadows. A toned ground speeds the process of painting, allowing simpler modelling and killing the stark white that otherwise would confront the artist initially."1
Colors for Grounds:
What color should you use for a ground? It depends on the subject and on you. Traditional colors for colored grounds include raw or burnt sienna, yellow ocher, burnt umber, and neutral greys. While various rules exist, you can use any color you like.
One rule is to use a warm ground for a painting dominated by cool hues, and a cool ground for a painting dominated by warm hues. Another to use the complementary color to the dominant color in the composition. Green for portraits (the complementary to red, a color used in mixing skin tones). One tip with oil paints is to wipe off the ground for highlights, letting the white underneath the colored ground show through more.
"...a mid-toned ground was popular for portrait painters... It allowed white chalk to be used for any initial drawing, and formed the mid-tones of the painting, allowing the lighter and darker passages to be speedily denoted. ...it gave the painting a unifying colour tone."2
If you use a wooden palette for mixing your colors when painting with oils, using a ground that's a similar color to the wooden palette means what you see when you mix is what you get when you put it on the painting, whereas a white palette can make colors appear darker than they really are.
"If you work on a middle tone, such as gray or light brown, it is easier to work up to the lights and down to the darks."3
Colored Grounds of Famous Painters:
The landscape painter Constable "favoured beige or mid-brown grounds. In The Valley of the Stour, with Dedham in the Distance, he left the reddish-brown ground uncovered in places such as the banks of the river. A coloured ground gives an overall warmer and darker effect than a white ground..."4
El Greco is supposed to have "scraped up the remaining wet colors on his palettes and used the resulting brown mixture of his grounds."5 Vermeer used light, neutral greys as his ground. "A consistently colored ground is important so that there is minimal influence on color perception and color mixing while painting."6
"In the first half of the nineteenth century is was noticed in artists' manuals that artists were increasingly using lighter grounds... 'These grounds never devour the color, as dark grounds do, in time'."7 The Pre-Raphaelites were amongst the artists opting for white-primed canvas and if they reworked a section of a canvas or fixed a mistake they would "simply apply more white as a local ground".8
Further Reading: Chapter Five of The Art of Impressionism by Anthea Callen (published Yale University Press 2001) is a 24-page, detailed investigation of ground colors and paint layers that looks at colored grounds vs white, browns palettes vs white, tinted grounds and pictorial luminosity/coloristic effects, and plein-air painting. The book is unfortunately out of print, and very expensive second-hand, so ask your local library if they can get it.
1. "Colour and Tone in Whistler's 'Nocturnes' and 'Harmonies' 1871-72" by Stephen Hackney. The Burlington Magazine Vol 136, No 1099 (Oct 1994), pp695-694.
2&7. "Pre-Raphaelite Methods and Materials" by JH Townsend, J Ridge & S Hackney, Tate Publishing 2004, p57.
3. "The American Artist Guide to Painting Techniques" by Elizabeth Tate and Hazel Harrison, Interweave, page 64
4. Colour, V&A Education (http://www.vam.ac.uk/school_stdnts/schools/teachers_resources/constable_resource/projects/colour/index.html), V&A Museum, London. Accessed 19 April 2010.
5. Alla Prima by Al Gury, p30.
6. "Uncommon Grounds" by Bill Berthel, Just Paint, Issue 17, September 2007, Golden Artist Colors
8. Townsend 2004, p60.