You can use white distilled vinegar (1 part vinegar to 1 part water), hydrogen peroxide (1 part peroxide to 4 parts water), or baking soda (1 part baking soda to 2 parts water) to whiten your laces instead of using bleach. A vinegar solution or baking soda mixture is safe on synthetic and natural materials. Only use a hydrogen peroxide solution on natural fabrics like cotton or hemp; refrain from using it on synthetics.