As you can see, the color in the upper-left frame changed, and it only takes one line of code:
parent.three.document.bgColor = colorname;
The value of colorname can be any color that you choose. But say you wanted to change the font color too, then use fgColor instead of bgColor. In fact, you can change any property of a frame.
I hope this helps you put frames more into focus, because even though they can be annoying as heck, frames can also be very usefull.