To quickly get started with adding colors to you products go to ADMIN | OPTION NAME MANAGER. Add the attribute name 'Color' and click insert.

Click on OPTION VALUES. selct 'Color' and type in the actual colors for the products; Red, Yellow, Green, etc. inserting after each color. Add all the colors you will need for all your products.

After you have your colors entered click on ATTRIBUTE CONTROLLER and select the product you wish to add colors to and click display.

Go down the page to ADDING NEW ATTRIBUTES and select Color on the left side and select the colors for the product on the right side of the box and insert. If you have the Improved attributes contribution you can select all the colors for that product at once and then insert.

There are of course better explanations in the FAQ and elsewhere in the forums but hopefully this will get you started.