I have noticed more and more students eschewing direct observation from life for their painting and in doing so slowing their efforts to be better artists and illustrators. Some of this is an over reliance on digital tools but not always. I see a lot of bad habits developing around color in particular. The biggest flaw I see most student work is monochromatic color strings for elements of the paintings and no interaction between the colors of the elements within the image.
I believe there are a few reasons for this.
They are making up the scene from their imagination without having enough of a mental library of images. An artist builds a mental library from working from life studying how light and shadow affects the color of objects and scenes around them.
They are using photos and video pulled off the web or other outside sources and have no understanding of the place or thing in the photo or video because they didn’t actually generate the reference. Photos are really bad at showing real world aspects of color and value.
They are coloring a black and white sketch, painting over the top of it without any modification of the hue and saturation of the color for light and shade. This lets the under drawing control the color which just lightens or darkens the chosen hue.
Color shifts from light to dark are poly-chromatic. That is the hue, saturation and value all change as the color lightens or darkens. These changes are altered by the angle, quality and color of the light source and all of the other lit elements in the scene that also act as secondary and tertiary sources of light.
It is up to the artist paint these transitions with understanding. This is why working from life is so important; careful studied observation is the quickest way to learn about color and light for a representational painter. I have used illustrations by N.C. Wyeth for this post because he had such a complete understanding of color and light his paintings glow.
Remember, all worthwhile theories started with careful observation, so if someone tells you that you need some complex color theory to learn about color, they are wrong. Theories can have their place in helping to clarify what you are seeing but in isolation without real world observation to back it up they quickly devolve into systems of formulaic painting.