Red is the colour that provokes the most physiological responses. It has been shown that red causes the human heart beat and blood pressure to rise and to aid the interconnection of brain neurons. It has also been shown that people working in a red environment work faster, but they also make more mistakes. It increases restlessness and nervous tension. Also, red is commonly regarded to increase appetite.
That red invokes strong reactions in humans is not so surprising when considering what is red in nature; fire, blood, ripe fruits.
Red is the colour that is most easily regonized, and the most visible in daylight. It draws attention. This is the reason why many traffic signs and warning signs are red. Red for stop signs are used all over the world.
Red is regarded as a hot, warm colour and it symbolize aggression and high energy. It is also a sign of warning, danger and error. In the Western World it is also a symbol of love and passion.
Variation and mixing
Pure red is a very bright colour which stands out both on a white and black background. Light tints of red can often look a bit unclean, and so then it can be a good idea to add some green to make it a bit more yellowish, or to add blue to turn it into a more pure pink. Darker shades of red can be appealing, and can be used very efficently on web pages.
It is also a well known fact that bright red and bright blue mixes very poorly. The reason for this more physiological – red is the colour with the longest wave-length while blue is among the shorter wave-lenghts. When viewing these colours the human lens has to adjust slightly to get them in focus. When you have red and blue mixed together the lens tries to focus on both, and it tires the eyes very quickly.
How to use red on the web
In general I think one can say that you should very rarely use pure red. It is a too bright and overbearing colour.
As said before, red is a good colour to draw attention. The first thought then might be to make your page red, to make people more likely to visit and read it. However, webdesign is different to other desing in the sense that when the visitor sees your page he has already made a conscious choise to visit it. There is no need to try to draw his attention further, but what you want to do is to keep his interest, and make him want to explore your page further. Red is not a good choise then, as it is not a relaxed colour, and the colour might draw attention from the actual content of the page. So this means you should avoid using bright red as the main colour of a page. Instead you can use red as an accent colour, to especially mark a part of your page that you think it especially important.
Red might also be an efficient colour to use in a banner, as then the whole purpose is to draw attention. I write “might” though, as it depends much on the look of the page that the banner is placed on.
On the other hand, a deep rich red can work very well for the main colour of a page – it conveys a feeling of something more classy and old fashioned.
A few examples
Pure red is often too bright and overbearing to use much on the web.
One is usually better of using a slightly darker shade of red.
Light tints of red can often look a bit unclean.
And it can be better to increase the green or blue component of it, to get a cleaner colour that moves towards orange or pink.
When mixed with yellow, red looks more brownish and move towards purple.
Combining red with blue will make the red look warmer and move towards the yellow.
Mixing red with black, grey and white is a classic colour scheme which has a sense of style to it.
Dark red and golden is a common colour scheme that is which also has a sense of class to it.
Or use it with a light cream colour.
A monocromatic colour scheme using only variants of red can be pleasing. Keep in mind that this is a very powerful combination, and it should be used with caution.