Colour Theory
Tone of Message.
Colours can be used to express emotions, and certain colours commonly represent specific emotions. When choosing your colour you might wish to considers the emotions they carry. This idea comes from Plutchick colour wheel of emotions. For more on the psychological effect of colours take a look at this webpage.
Following a similar idea, colours are sometimes said to feel "Warm" or "Cool" - this is an idea that is popular in wall paint especially - a blue room feeling cold etc.
Corporate Colours / Corporate House Style
Companies, organisations and brands often have their own preferred colours that are commonly used on most things to do with that organisation. These are called House Styles. For example Lakelands Academy's colours are mostly Dark Blue and White, with the four colours representing the four Meres used a bit as well. - red, green, yellow and blue.
These House Styles often override a lot of the creative choices of colours for promotional material - McDonalds have to use Red and Yellow because that is what everyone expects.