Hi Cynthia,
Unfortunately, the science does not support the claims of the topical die/tint/etc sellers on improving how well laser works on grey, white or light color hair. The most effective of those products is Melanin-encapsulated liposomal spray (lipoxome), but it only helps by 10 to 14% and significantly increases the chance for side-effects. (to even get this marginal gain required six applications a day for 8 weeks!)
As a late bloomer, you likely have well established facial terminal hair growth (I'm in the same club).
I expect that you will need electrolysis for your facial hairs, especially the grey hairs that you want gone.
Laser is often more effective on dark body hair than facial hair for us late bloomers (YMMV).
Please keep in mind that genetic females typically have hair on their face, chest, arms etc, but without androgens,they remain as vellus hairs.
To permanently remove hair, the stem cells at the root of the hair must be destroyed.
Effective laser treatment of male pattern facial hair requires a black hair root bulb, light skin, the appropriate laser light frequency and a very skilled operator. (facial terminal hair follicles formed on testosterone typically have a larger and longer root than those found on genetic females)
Use of a laser to perform photothermolysis (I.E. light to make heat) is only effective when the energy of the laser light is quickly absorbed by the melanin at the root of the hair, and transferring enough heat to the stem cells to kill them. Too little heat stuns them and they come back, Too much heat and you damage the deeper layers of the skin and/or the sebaceous glands. Wrong laser or incorrect use can in some cases induce hair growth.
IPL treatments can be more damaging than laser, as the broad spectrum light heats everything.
Electrolysis is the only permanent hair removal method, all other methods are temporary.
Electrolysis done by a licensed professional uses a very fine metal probe that is inserted alongside the hair shaft down to the root and uses direct current to generate lye that kills the stem cells or a microburst of Radio Frequency energy to heat the stem cells or a combination of the two.
Best Wishes for the New Year
-Cindi
P.S. Apparently I'm feeling professorial this morning even though I have never been one...
The wikipedia article on "hair follicle" "Terminal hair" "Vellus hair" "Laser hair removal" and "Electrology" are good stating points for more information.
