Imagine if you will a custom sheet of paper that uses three assets.

1. The image that is placed on the paper.
2. A png that maps out the elements
3. A small script file that tells what each color represents

For example: http://imgur.com/a/cCoT3

Such a script can be really basic borrowing a modified syntax from css.

Code:
#000000:textbox
{
font-family: "Times New Roman";
font-size: 20px;
text-align: center;
}

#0eff00:checkboxdefault
{
background-color:none;
}


#0eff00:checkboxclick
{
background-color:"#000000";
}
From that each color get's it's own property that can be modified by clicking on each of the elements much like a html page on a tablet.