Highlights, Lowlights and Color Glaze
A: The length of time you should wait depends largely on the condition of your hair. Any chemical process can have an adverse affect on your hair, and applying a color process on top of hair that has already been subjected to a chemical process runs a higher risk of damaging the hair. This is doubly true of processes that lighten the hair's color.
Even if the idea of a color glaze is not for you, you should consider giving yourself at least one deep conditioning treatment before you attempt to have your hair re-colored. This will help to restore any moisture lost to previous chemical processes, and protect the hair from future ones.
Finally, given your dissatisfaction with the color results of your last highlight/lowlight procedure, you will want to speak at length to the stylist who performs the new color processes for you to make sure you are getting what you want this time in the way of color results.
Discuss things like size of the highlighting and lowlighting; the spacing of the strands of differing color; and the colors being used themselves. I would hate to see you undergo a second dimensional color process and still not be happy with the color results.
©Hairfinder.com
See also:
How to color hair
After-care for colored or chemically treated hair
How long should I leave my hair until I get it highlighted again?
How can I remove my highlights? Can I use a de-toner?