Hi ruskenb,
the easiest way to achieve this would be to edit any of the existing color styles that you don’t use, such as, for example, light orange.
To do this, you should open file light_orange.css, located in css/colors/ directory of your template directory and change the color codes according to your needs.
To change the color of the background of the page, simply overwrite body-bg.gif image located in /templates/ja_rasite/images/light_orange/ directory with the image of appropriate color, or upload a new one in the same dir and change the filename in css according to that.
This should be a fairly easy task. I would recommend you to use Firefox in combination with Firebug extension for a better understanding of the template structure.
If you need any further help on this, please don’t hesitate to drop a line here!
Good luck! 🙂