I would use a can of spray paint in your favorite color choice.
Paula....I sprayed mine years ago and covered the top with foam then purchased fabric and now its a cut stool with storage. It was about to use screws to hold the cushion with fabric. Good luck!
Use a spray paint for plastic inthe color you would like.
They make spray paints now for plastic. Be sure when you purchase it, it mentions it is made for plastic. They have them in all colors now, so you will probably find the color you need and spray painting is less fuss, in my experience. Hope this helps.