Updated on 22 February 2017 (Harvard referencing).
18 April 2016. Since I know perfectly well, and was reminded of this in the course feedback for Drawing 1 (with the result for which I was very happy, even if not taking into account the circumstances), that I need to rush less my projects regarding preparatory sketchbook drawing, experimentation with setups, comparisons with other artists and such like, I decided that I would need to investigate the style of some artists before starting my own painting.
I have always been drawn to paintings where the outlines of the depicted objects are clearly visible, sometimes in black, sometimes in hues corresponding in some way to the colour(s) of the object itself, as e.g. in Vincent Van Gogh’s famous self portrait (Fig. 1). He did not only use a darker tone of an object’s colour, as in his hat, to paint the outline, he also appears to have taken care to choose a complementary colour to paint the background: bluish hat – orange background, green coat – red background. This means, according to Chevreul’s colour theory, that the complementary pairs will reinforce each other, while other colours will not. This also means, if I am right here, that by choosing the mentioned colours van Gogh’s figure raises from the red-orange background without having to add perspective.
The same effect should, by the way, be working in a painting by contemporary artist Denis Castellas, who I first read about in the book Vitamin P (Schwabsky, 2002, pp. 62-63). The painting, (Castellas, 2001) shows a lady in a red and green coat before a grey background.
Another artist working with outlines was Henry Matisse, a very famous example of which is shown below (3). His style appears less consistent than van Gogh’s with respect to colour theory. While the left side of the picture appears to be in one image plane apart from the hair, the right side is clearly divided into background and foreground by the dark layer of colour separating the red dress and green background.

And another example I particularly like, by impressionist Samuel John Peploe (1871-1935) (4):

In the above example I find good ways of using outline in grey and white objects. I will have a very close look at the choice of colour and line in Peploe’s painting and attempt something similar in my own picture.
Resources:
Van Gogh, V. (1889) Self-portrait with Bandaged Ear [oil on canvas] [online]. [collection Mr. and Mrs. Leigh B. Block]. [Available at: https://commons.wikimedia.org/wiki/File:Vincent_Willem_van_Gogh_106.jpg [Accessed 22 February 2017]
(2) Schwabsky, B. (2002) Vitamin P: New Perspectives in Painting. Phaidon Press.
(3) https://en.wikipedia.org/wiki/Green_Stripe and https://en.wikipedia.org/wiki/Green_Stripe#/media/File:Matisse_-_Green_Line.jpeg