How to add coloured dividing lines between content blocks

Site URL: http://www.staysixact.com.au

Hi team, for viewing purpose, I am trying to add a colourful dividing lines between content blocks in any given page. How can I do this? 

Many thanks in advance.

This may not be exactly what you want, but its still cool. 

from a complete newb, Becca has great tutorials that are super easy to follow. This is just one example of a great vid