If they're the polyester/cotton blend coveralls then you won't be able to lighten them to anything close to that color. I know cuz I had a pair and even washed them with a gallon of bleach with no luck. All I was able to achieve was a very slight fading to the navy blue. But if you have any luck using something else, let us know.
If you want something close in a premade coveralls you'll have to get a pair of Red Kapp coveralls. Postal blue I think is the closest color they make.
Hope this helps,
Cruzer