The file that gets the most attention when you are modding a WordPress Theme is the CSS stylesheet. It is like the brain of the whole Theme and whatever is included here controls how your Theme will look in the final appearance. Thus it is vital that you understand at least a little basic about CSS before attempting to customize your WordPress Theme.
By understanding the basics do not necessary mean you have to go and memorize every code structure. Though it would be really helpful if you can, we noobs will quickly lose all interest if we were to learn all those mind boggling stuff. As long as we know what to change and where to change it, then modding can be lots of fun.
This easy to follow Video Tutorial will show you how you can easily pick out the colors in your Theme and how to look for the right spot in your CSS file to change those colors.