Colour Theory

Just like composition, colour within a concept image is extremely important when it comes to forms and objects reading well. As my 2 dimensional art pursuit had started (and indeed remained for many years) in black and white graphite drawings, I essentially had to learn colour theory and the magnitude of its importance from the ground up. What follows is just some of what I have learned about implimentation of colour in 2D art.

Many of us were told in primary school of the basics of colour theory. In artistic terms, there are 3 Primary or First-Order colours; Red, Yellow and Blue. From these, there's an additional 3 Secondary colours (Orange, Green and Purple) created by combining 2 Primary colours. There is also a range of Tertiary colours created by combining a Primary and Secondary colour in varying amounts.
What is less often taught is how different colours work better together than others, and how effective colours are in setting mood and atmosphere.
There are several ways of combining colours to appear aethetically pleasing. One of these is using complementary colours. These are 2 colours that are opposite one another on the colour wheel. A general rule of thumb is that placing a complementary colour within its matching colour will make a focal point, as it's the highest point of contrast. Complementary colours often have different intensities, which means that to balance one intense colour, you would need to use more of its less intense match within the image to create pleasing balance.
Analogous colour schemes are another style of colour composition in art. This is a far less intense and high-contrast method than straight complementary colours. It involves choosing 1 colour and 2 others which are on either side of it on the colour wheel. The more relaxed nature of the colours often allow for more viewer immersion withing the image, as it's less harsh on the eyes, and hence more pleasing to look at.
Analogous colours can be seen in this painting that I created for our game project.

 As you can see, almost all the colours within the image's atmosphere are around red, purple and dark orange. The only exception is the high-contrast (almost complementary) blue on the protagonist. This is to draw attention to her. High contrasting colours can be jarring to look at, but can also be very useful for drawing attention to points withing an image if used sparingly.
There are other colour mixing methods (split-complementary, triadic, etc.) and many more colour management styles that I haven't mentioned. Altering levels of saturation with colours can create even more complex colour schemes.