Change bg colour to random value from array

Could you please explain for a beginner how I would achieve the following:

I have five defined colours.
When user refreshes/loads the website one of these five colour values is displayed at random


Something like these perhaps?

Jquery: random background color
Random color in jQuery
Random predefined background color and text color on 2 divs

If you need more help, please provide the information requested in this post: Posting Guidelines for the Code Help Category