Wash the item according to the washing instructions for the material, in hot water, if possible. Wash using 1/2 tsp. of Synthrapol detergent per pound of fabric. A specially formulated detergent, Synthrapol helps to extract excess dye and is safe with silk and wool. Often new fabrics still have excess dye, which will rinse out in the first washing.
Sun-fade the item if washing has not achieved the desired level of lightening. Hang it outdoors in open sun from clothespins or a hanger. Leave the item for one to three days. Rotate it if it seems that one side receives less light than the other.
Create a highly-diluted solution of bleach and cold water for further fading if sun-fading proved insufficient. But first, check the material instructions to see if the material can accept bleach. Test a scrap piece of the same or similar material, if possible. Soak the item in the bleach solution for a few minutes. If bleach is not an option, try soaking the item for longer in vinegar and water or baking soda and water. Commercial color lighteners are also available.