Colour consists of three elements: value (odtien), hue, and chroma (intenzita). You choose from all three of these elements when using a colour picker in Photoshop:
Every colour comes with baggage - emotions and connotations that we get from nature, from society, from science, etc. The colour of an object changes how we think of it, because of these mental associations. A white swan feels more pure than a brown duck, a red rose expresses love better than a yellow one. A black crow feels meaner and dirtier than a budgie. This is called color symbolism, and it's very strong, even though it's false.
Some psychologists use these connotations to evaluate patients, such as children, by what colour crayons they choose to draw with. Blue means depression, red anger, yellow fear, purple inferiority, orange immaturity, pink weakness, grey depression, and black menace. The only healthy colour a kid can use these days is green...
I hope you can all see the folly of judging someone's mental health before they've even started a drawing. I mean, if they're calm enough to sit down and draw something, that's a good sign. And, it's crucial to remember, despite all the possible meanings that colours can have, the context is key. A red rose and red blood are not the same thing. So, here's the baggage:
1. White and light backgrounds feel like day, so they feel safe, because we see well during the day. White symbolizes light, life, and hope.
Alcove, by Eva Gonzales
It's hard to imagine any monsters hiding under this bed.
2. There are exceptions, based on context. The arctic is white, but very scary because the cold can kill you, plus polar bears. If we're escaping from prison, a white spotlight becomes terrifying.
Holiday, by Zach Graves
Cold and isolation can change the meaning of any colour.
3. Black represents darkness and mystery, so a black background feels scary and tense.
Diner, by Mikko Kinnunen
Mothers, by Kathe Kollwitz
Portrait of a Young Man, by Giovanni Boldini
The black background above gives a sense of mystery to the man in the portrait, making him more interesting. We don't know where he is. Our only information is the introspective look on his face. What's he thinking?
4. Bright shapes tend to glow more in black backgrounds. If you link your darks together, "shapewelding" them, they can frame your light areas and make them stand out.
Story Time, by Elin Danielson-Gambogi
Note how the man's coat, his chair, and the shadow under the table all merge together, so that you look up at the contrast of the lamp and the woman's face.
Here's another simple example:
Girl in a Black Hat, by Giovanni Boldini
Notice how her hat and clothing blend into a black background?
5. Part of this has to do with simplifying your value scale to only 5 or so values. A painting that does this has "breadth". The fewer separate values you use, the clearer it becomes.
Choco Jungle Sketch 3, by Luc Desmarchelier
You can limit down to 3 or even 2 values. It's a trade-off between clarity and realism.
Sketch by Louis Glanzman
6. Both black and white can symbolize death. We wear black to funerals, but in India and Korea, they wear white. Bones are also white.
7. Red reminds us of blood and fire.
Rib of Beef, by Gustave Caillebotte
Face Lit by Fire, by Laura Sanders
8. Yellow reminds us of the sun.
Yellow Sea with Small Steamships, by Emile Nolde
Anything that's yellow gives us this same sense of energy and joy.
The Little Yellow Horses, by Franz Marc
9. Blue reminds us of the sky and water.
Departure-Arrival, by Rachel Constantine
10. Objects that have the same colour and/or shape in a picture also connect together. But the connection to colour is even stronger.
Huntsman & Herdsman, by Katherine Stone
Do you see how the cat and the boy seem to belong together in the painting above? Notice that they have the same colour hair. Would the two have such a close, loving relationship if the cat were some different colour? Would you immediately read them as being a family?
11. Value is the most important to the success of a composition. Great colours can't save a poor value design with no tonal structure. Think of the design in only black and white and see if it works. Then it'll still work with a full range of colours and values. It will read well even from a great distance.
The Offering, by Steven Hickman
In the painting above, Steven Hickman begins with a black and white sketch, then paints his idea in black and white on a canvas, and then adds colour at the end.
12. James Gurney argues that a subject is more pleasing when it satisfies what he calls the windmill principle of value, based on Rembrandt's famous painting of a windmill.
The Windmill, by Rembrandt van Rijn
If you look at each of the four sails, and compare it to the sky value, you'll find each is different: light against light, dark against dark, light against dark, and dark against light.
It's a great way to marry a subject to its background. It gives a sense of complete interaction, every piece contrasting in a different way, like a motif in a Bach fugue.
13. If that's too hard for you, a simpler idea, common in landscape painting is to change the lighting of the foreground, either to or from light to shadow. This emphasizes depth, and is a great way to create focal points (see next lesson).
Grove by a Pond, by Ivan Shishkin
Forest Interior, by Ivan Shishkin