Red is the colour of fire and blood.  It is associated with energy, war, danger, strength, power, determination as well as passion, desire, and love.

Red is a very emotionally intense colour. It enhances human metabolism, increases respiration rate and raises blood pressure. It has very high visibility, which is why stop signs, stop in traffic lights, and fire equipment are usually painted red. In heraldry, red is used to indicate courage. It is a colour found in many national flags.

Red brings text and images to the foreground. Use it as an accent colour to stimulate people to make quick decisions; it is a perfect colour for 'Buy Now' or 'Click Here' buttons on Internet banners and websites.

Red is often used to evoke erotic feelings (red lips, red nails, red-light districts, 'Lady in Red', etc).

Red is widely used to indicate danger (high voltage signs, traffic lights). 

Light red represents joy, sexuality, passion, sensitivity, and love.
Pink signifies romance, love, and friendship. It denotes feminine qualities and passiveness.
Dark red is associated with vigour, willpower, rage, anger, leadership, courage, longing, malice, and wrath.
Brown suggests stability and denotes masculine qualities.
Reddish-brown is associated with autumn.