Lasers work on the basis of the color of the target, your hair, as opposed to the color of the light from the laser. If you have no color in your hair there can be no results. White, red, blonde hair will not respond to laser treatment. If you ever put some red cellophane up to your eyes as a kid, the world did not turn red. What happened is the cellophane acted as a FILTER and filtered OUT ALL COLORS EXCEPT RED. What you saw was the red component of the white light of nature. This is true for each color filter because WHITE LIGHT IS MADE UP OF ALL COLORS. White is the presence of all colors and black is the ABSENCE of all light, therefore, no color. We see reflected light but black does not reflect light so it appears as NO COLOR OR BLACK. If you use a red filter and/or red laser… only red is allowed to come through and RED hair allows red lasers to pass through with no effect. This is the same as going into a black room and putting a strong flashlight into your palm. When you look at the other side of your hand you will see red skin and darker areas where the light is not strong enough to pass through. Blood is red and allows red light to pass through but no other color. If the light is not strong enough it will not be intense enough to pass through except where the skin is thin enough as where fingers meet. The energy in the light converts to HEAT when it hits a target that is the OPPOSITE of the color of the laser. It takes a few lasers to treat all situations because there are so many colors of skin and tattoos. Obviously, there is much more to this but for now this is the basics.
Also, each color light is expressed as a particular wave length. No two colors have the same wave length, therefore, the ONLY reason to use any one particular wave length over another is based on the COLOR of the target you want to treat. If there is a TUNABLE LASER that can give you multiple colors it would have more value as it, theoretically, could be used to treat more subjects with varying colors but they have to be the opposite of the target whether it is skin or hair.
If you use a greenish-bluish laser it will VAPORIZE the dark colored hairs it comes in contact with. The skin has to be shaved because the hair above the skin line will vaporize and might burn your skin as the hair is against the skin and much skin has color in it that is similar to the color of the hair but not as concentrated. That is why the best results are seen in patients with dark hair and light skin that has less or little color. By removing the surface hair the laser will seek out the color it works against and that is the tips of the shaft that is flush with the skin surface and visible but only if the laser is intense enough to pass through the skin to the depth of the papilla with enough light to create adequate heat at the depth of the papilla. All papillae are not at the same depth like on a plane or flat surface. They are each at a different depth. This varies from hair to hair, not by much but by enough to make a difference.
That is enough for now. I am getting tired and make too many errors that have to be redone. I am a hunt and peck typist.