There is a lot to say about color theory, but I won’t do that. :) I will keep it relatively short and explain how you can exploit the basics of color theory and color harmony theory to create a photo that is more appealing to the eye.
The history of color theory goes back to (at least) the 18th century, when it was believed that all colors could be created by mixing the three colors red, yellow and blue (RYB). These three colors are called primary colors. In the late 19th century, scientists found out that the best primary colors for the human eye are actually red, green and blue (RGB) instead of RYB. The reason is simply that combinations of RGB lead to the greatest range of colors visible to the human eye. Secondary colors are colors that can be created by mixing two primary colors. For the RGB primary colors, the secondary colors are yellow (green + red), magenta (red + blue) and cyan (blue + green). The tertiary colors are combinations of primary colors and secondary colors.
The so-called color wheel is a schematic organization of the primary, secondary, tertiary colors and other colors that can be created from the three primary colors. The primary colors are equally spaced around the color wheel. In books and on the internet you might mostly find the color wheel for RYB primary colors, but here I use the RGB color wheel as RGB are the best primary colors for the human eye as explained above.
RGB color wheels
So color theory has a long history. The theory and research on color harmony is also quite old and research is still ongoing. Let me first explain what color harmony actually means. Color harmony refers to the property that certain combinations of colors are aesthetically more appealing than others. The research that was done on primary colors and which are the best to the human eye I consider as hard science: the research was quantifiable and objective. Color harmony theory however, is much more soft science. There is no theory that tells you exactly what color combinations to use to make the most appealing image. Some color harmony theories are contradictory; there is no consensus about color harmony. And one of the main reasons for that is probably that color combinations that are aesthetically most appealing are dependent on human race, gender, age, culture, etc. Basically, what is aesthetically most appealing differs per person. However, the good news is that there are some basis rules for colors combinations that are on average aesthetically (most) appealing.
Color combinations that are aesthetically appealing include combinations of:
- Complementary colors, i.e. colors that are opposites on the color wheel
- Split-complementary colors or compound harmony colors, i.e. a variation of the complementary color scheme
- Triadic colors, i.e. colors that are equally spaced around the color wheel
- Analogous colors, i.e. colors that are adjacent on the color wheel
Adobe Color Themes panel
How to use color themes in Photoshop? Photoshop has a great extension called Adobe Color Themes. The panel can be accessed in Photoshop as follow: select Window > Extensions > Adobe Color Themes. The color rules described above are included in Adobe Color Themes. You can use Adobe Color Themes to both check the color scheme of your image or you can use it to help you adapt the colors of your image according to a certain color scheme.
For four of my photos I have shown how the color scheme looks like. The first photo has the complementary colors scheme, the second the triadic colors scheme, the third photo has the analogous colors scheme and the fourth photo has the compound colors scheme. If you want to change the colors of your photo, simply use the standard techniques to change colors in Photoshop or add colors by, e.g., creating a new layer using blend mode ‘soft light’ and use a brush to paint in certain parts of the image with the appropriate color.
And in this way, using these color schemes, you can create images with color combinations that are aesthetically more appealing. However, use these color schemes as a guideline and not as a strict rule. Deviating a bit from this schemes might result in even more appealing images, but be aware that deviating too much might result in color combinations that are perceived as ugly.