Background colour change like a carousell / every 20 seconds

Hello, 

Firstly thank you anyone who takes the time to read this. We are new to Squarespace.

I'm designing a website for a friend and she would like the background colour to change constantly. 

4 pastel colours, pink, yellow, green, blue... 

Either the background changes colour:
a) on a timer (like a carousel)
b) or every time a new page is opened

Is this possible? 

Thank you for any help

Rebecca and Claudia, 
London