Hair Color Notes

Green neutralizes or cancels out red.
Blue neutralizes or cancels out orange.
Violet does the same for yellow.
And vice-versa.
So....
If your platinum blonde clients hair looks too yellow you would use violet to tone or neutralize it.
Some would think which violet should I use?
First, examine your clients hair thoroughly. Next, determine what level the hair is. Some seem to think to grab any violet off the shelf and use it, but if you don't know the law of color you could really make a mess. You should use a violet toner that's the same level of the hair or at the most, one level higher.
Now back to the law of color, always remember that porous hair GRABS ash and rejects warmth. If your clients hair is porous you run a great chance of the hair turning a smoke or grayish color. This is why it's so important to not use unfounded short-cuts and not to compromise the integrity of your clients hair no matter what service you're doing.
Correct application and the usage of the correct products is very important at all times.