Not much info to go on here so I'm not sure where you're having problems.
Have you read the documentation on this site? http://www.concrete5.org/documentation/using-concrete5/dashboard/pa...

Remember, you can drag and drop the little circle indicator to change color, then you need to click "Ok" on the bottom right of the color picker, then click "Save" your edits. IMPORTANT - Lastly.... clear your cache both on the site and your browser or your color change will not be immediatly visible.
Let us know if that works

Thanks very much. That solved it. I guess the problem was that I didn't know how to use the color picker. I didn't realize that you were supposed to move the little circle. I tried clicking on it and tried to move what I thought was a control on the vertical bar to the right of the color wheel. Your information was very precise and helpful. Thanks a lot. I did have to clear the cache on the website and the browser.

Rich

Happy to help Rich. There are more precise color settings available also (like typing in the RGB codes etc.). Fun is in the exploring :)
Feel free to mark the advice as "Best Answer" if you think it will help others