Re-Intensify Highlights

Purple hair dye
Photo: Nikolai Kazakov/Shutterstock
Q: Okay, so I recently got my hair professionally colored at a salon. It is mostly a very dark espresso brown with some eggplant and a tiny bit of burgundy-type color in it, demi-permanent so as not to damage my hair as much. I also have (what used to be) bright purple highlights. I loved the way it looked at first, but I have only had it for one month, and the color is already faded. What a bummer!
I've been sure to be very gentle with it limiting shampooing to maybe twice a week with a color-safe shampoo in addition to washing it with cold water and using thermal protectants, but my highlights have faded to an almost light brown looking color.
My question is: What would happen if I used a bright purple hair dye, such as Manic Panic gel, over my entire head? My goal is that it would re-intensify my highlights and add a more purple tint to the rest of my hair. Is this realistic?

A: The application of a demi permanent color like Manic Panic will likely tint all the hair on your head, but may even out the lightness levels of the hair and make it look all more uniformly colored. It depends on the specific shade of the Manic Panic.
If your goal is simply revitalizing the highlights, you could enlist the aid of a friend and apply the color just to the highlighted hair using foils to isolate the color.
You should be sure, however, to talk to your hairdresser about the color fading and discuss the possible causes. It may be that the salon would be willing to do something to "fix" the faded hair for you.
At the very least, you want to make sure that you're not going to experience unexpected chemical interactions from the color formulas they have already decided to use.
See also:
Highlights Q&A
Highlighting with foils
How to make hair color last longer