When you foil with color, formulate your color one level lighter than the target level. For example, if you want to end up with a level seven highlight, mix your formula as though you want level eight highlights. Since the color is processed in foils, it’s not going to oxidize enough, and your highlights are going to end up a little lighter than they otherwise would
In similar fashion, when doing lowlights, I like to formulate a level darker to add some dimension to the existing color. If the color of the lowlights matches the existing color precisely, it will look too monochromatic.
Highlights and lowlights should be at least two levels apart from the background color in order to be visible.
When highlighting with color, remix your formula every twenty minutes. The trick here is to put the tint and the developer together in the bowl but don’t mix them until you are ready to apply.
You don’t need many foils to create special effects. Remember that highlights are just that: highlights. Fifteen to twenty foils are enough for partial highlights; quite often the desired effect can be achieved with ten to twelve foils. Thirty to thirty-five foils should be plenty for a full head.
Concentrate on the visual area of the head: the top and the front. That’s what everyone sees.
Stay ¼ inch away from the scalp to avoid bleeding. Remember that the thickness of a slice or a weave will influence the distance that you should stay away from the scalp.
There is a great technique called shadowing when you put highlights and lowlights in the same foil. The results are very impressive. Another way to do it is to weave highlight in one foil and then put pieces of the same weave into a different packet. You will have two back-to-back foils.