User blog comment:Glenn31/Hurt and Heal 2: Electric Boogaloo/@comment-27126228-20151227080432/@comment-2066983-20151228150609

You need to right click the part you want to change color, click Cell, then Cell Properties, then where it says Background Color you type in the code for the color you want to use. For red it's rgb(200, 8, 21)