M.P.
Polyester fiber is made the color it is. It is not dyed. There is nothing you can do to change the color. Polyester fiber cannot be dyed: therefore you can't dye it white.
It is easy to make a skirt. Buy some fabric. Sew the ends together. Make a casing along one side in which to insert elastic. Hem the bottom. Viola, a red skirt. I suggest you could find someone to do this for you for not much. Ask at a fabric store.