Changing the entry background of specific fields only

Hi

I am trying to alter the background colour of specific entry fields in a form from the standard pale blue (HEX: #CCD7FF) to a Yellow colour to make it stand out to people who have to enter information into the form.

I have created the following javascript, which I have cobbled from a number of different sources and put it into the Custom Calculation Script section of the Field Properties, but it isn't working:

var theBackground = null;

function setBackgroundColor = ["RGB",204/255,215/255,255/255];//(HEX:#CCD7FF)
{
theBackground.setColor(new Color(["RGB",253/255,202/255,11/255];//(HEX:#FDCA0B)));
}

Can an expert in Javascript help me with the above so that it works?

Thank you in Advance.

Nicole