So we're going back to art class today - everyone remember the color wheel that we learned in grade school? This is the very basic of what I do when it comes to hair color.
First off, there are 3 primary colors - Blue, Red, and Yellow. The American hair level system is 1-10, 1 being black, 10 being pale blonde. Each level has a 'remaining pigment' that is revealed when the hair is lightened.
For example, when you lift hair from being black, it goes through different levels. On the color wheel, start at blue, and work counter clockwise around. Darker colors appear dark because they have larger molecules of dye, blue being the largest, therefore the darkest. As you lighten, red is the next largest primary color molecule, so that begins to show through next. Red is the hardest to get into the hair shaft, and also to get rid of. Because the human eye views it with such certainty, either you love it or hate it.
Level 6 (light brown)'s remaining pigment is Red. As you lift from light brown to blonde (for highlights), you go through an red-orange, orange, and yellow-orange stage. This is the part of the coloring process that most people dislike getting 'stuck' in. No one wants brassy orange highlights, so to get through that, you just have to either pop it up to level 9 or 10 (remaining pigment yellow = pretty) or tone out the unwanted pigment.
Tone = color glaze = toner = demi/semi permanent color - it's all the same thing. To neutralize the unwanted color, you just go opposite of the color wheel. So if you look at the red color above, the opposite across the circle is green. If you look at the blue color above, the opposite is orange. These are called Complimentary colors.
Color is one of my favorite services to provide for both men and women because it can change the appearance of someone so dramatically, for better or worse. I always try to keep in mind the person's eye color, skin color, and how much they want to maintain their look. So you can either use just color, foils, or a combination of the two, foil with color. Personally, I feel that foil with color gives the most options because it's very multi-dimensional.
Last but not least - please do not attempt this hair color theory process at home by yourself! Because when you end up with black on your hair and decide that it was a mistake, we have to go through all those levels of color to get it out. It's impossible to just put a lighter color on top of a darker color and expect beautiful results. Think - Easter egg coloring.