How do you get rid of facial hair without it growing darker?

NO removal methods (such as shaving, waxing, plucking, laser removal, threading, or using depilatory creams) will EVER cause subsequent hair growth to be darker, unless the preceding hair was bleached artificially or by extended sun exposure. To lighten hair, commercial hair peroxides, lemon juice, sun exposure, and certain prescription medications such as Vanica may be used, though not necessarily without side-effects.