Colour, the reflection of light off of an object causes this phenomenon. Colour is in everything we see everyday and affects us without our knowing. Different colours affects our moods and emotions differently, for example yellow can leave you anxious and blue can keep and calm or sadden you. However, colours can also have a different affect on you personally because of an experience you might have had in your past. One can tell a lot from the colour that somebody wears, for example red shows confidence and for a lady is very sexy, and for a man blue would be stable (we all know how women love stable men). – http://www.scienceofpeople.com/2013/01/10-ways-color-affects-your-mood/.
Colours have different meanings in different parts of the world and different cultures as well. In Japan black is see as a colour of honour and white is seen as a colour of mourning whereas, in the western world, black is the colour for mourning and white is seen as a colour of purity (http://blog.teamtreehouse.com/how-colour-communicates-meaning) which is why they are always having white weddings. Other examples include the colour red which in India is seen as purity again, in China it means good luck and in the west it means danger, love or passion. In Egypt the colour for mourning is yellow whereas in the west it symbolizes hope and courage in Japan.
So as you can see, colour can mean so many different things to a person all because of their culture or emotional background.
If you would like to know more about the psychology behind colour you can click here.