1. Open Paint. (start- all programs- accessories- paint) See the colors at the bottom/top/side of the screen? You're not stuck with just those.

2. Click on Edit- Custom Colors- Define Custom Colors. Now you can change it to any color you want.

3. If you get a color you really want to keep, click on Add to Custom Colors. Then just click on Colors- Edit Colors again and you can click on your custom color.