If they use cotton and if the dye has enough yellow, it shouldn't be too hard. The panels that mainly need bleaching are the back and lower hemline panels. (There are varying degrees of bleaching on the other panels, depending on which jacket you are looking at, but those are the most critical and consistent throughout all screen copies.)
The easiest method I found was to spray bleach with the same kind of spray bottle used on plants. Misting it from the top and downward, getting heavier the lower you go. Then pour warm water from the top down and make the bleach "flow" through the fibers, until you have effectively washed the fabric clean of bleach. This will give you a fairly even gradient.