Red is the colour of fire and blood, so 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, stoplights, and fire equipment are usually painted red.
In heraldry, red is used to indicate courage. It is a colour found in many national flags.
Source: Colour Wheel Pro