I got the idea for an article about the colour green when I saw Sergio Leone the Second lose his lunch (or his breakfast—he always eats the same thing anyway) after too much wheel running. Green—a colour that evokes playful rolling in the grass, or a tree trunk as seen by the colour-blind.

Let’s begin with a few facts about green. The wavelength for green falls between 520 and 570 nanometres (who knew?). In the human eye, M-cone cells (M for green, of course) respond to stimuli within that frequency and allow us to see this cold colour. In fact, all those visionaries who report ET and “little green men” sightings are supposedly endowed with a higher-than-average number of M cones! Green is not considered a primary colour in the subtractive colour model (CMYK), but it is in the additive model (RGB). If you’re wondering what that means, the additive model is used to define colours as emitted by a light source, whereas the subtractive model is the process by which the absorption effect of two or more colours is combined to create new colours.

Green is located between blue and yellow in the colour spectrum (and between “Greek Orthodox Church” and “green algae” in the dictionary). That’s why it has the soothing qualities of blue but also the energizing properties of yellow (with a hint of red’s rage).

According to Reader’s Digest, green is the easiest on the eyes as far as colours go. It is both relaxing and refreshing—which is why most hospital walls are green (no, it’s not a ploy on the part of overextended nurses to go unnoticed by hugging the walls).

Green has much cultural significance, both positive and negative. Green represents growth, renewal, hope, and abundance. Green also represents envy, jealousy, sickness, and even death. Green has become the symbol of environmental protection and social justice—we need only think of the Green Party or Green Peace (but not the Green Goblin).

In Web design, green correlates with richness, stability, and nature. Many great designers (such as myself) use this colour to create call-to-action buttons, since it is proven that green buttons get more attention, not to mention more clicks than any other colour. Green maximizes readability and minimizes optical fatigue, which is a crucial factor in Web design. But watch out—too much green can have a harmful effect and create jealousy! It’s important to get just the right dosage.

Here are a few examples of sites that use green well: Heineken, The Bug World Experience, Mint and COBA Hair.