Before putting something in a dark color out where it can get rained on, try ironing a sample first against white muslin using the hottest iron the fabric can stand and heavy steam. If there is any excess dye on the fabric, you will see a color transfer to the muslin. If there is a color transfer, you can try washing the items with a couple of cups of ordinary table salt and then retest. Most times, the salt will do something to the dye and it will stay firmly adhered to your fabric.
I learned this years ago from a Fieldcrest towels rep and now I automatically wash all my new towels this way before I use them. I haven't had a color bleed problem in years.