Unless you are using highlift blondes no color over the counter will be 12% peroxide. That is 40 volume! Even as a colorist, I don't use 40 volume all that much. Also, there is ZERO reason to ever use any permanent color on a hairpiece. When depositing color, (which is all you can really do to systems because the hair is treated and will not lighten predictably,) demi permanent colors, especially the professional ones (and even the lesser quality ones found at Sally's) produce beautiful multi dimensional tones in the hair as they are slightly translucent in nature on not opaque. Demi permanent colors do not lift. Demi's are longer lasting than semi permanent colors and basically the same as semi permanent color but made with permanent color molecules without the alkalinization ingredient. Semi permanent color is now a term that "usually" refers to a single component color.

In addition, a two component color (2 bottles mixed) has little to do with its natural hair lifting ability simply because of the presence of peroxide. The peroxide only acts as a color molecule oxidizer unless there is an alkalinization agent present such as ammonia or MEA at which that point the natural hair color will lift. It is this alkalinization agent that determines if the color is "permanent" or a lifting color not the presence of of peroxide.

Sorry to get a little technical..but knowledge is power