Turning your gray hair into highlights is a fairly easy process. If you have dark hair, the highlights might come off as extreme since you have to make them very light to incorporate the gray. Gray hair does not absorb color the same way as pigmented hair, making it better to find a color that blends with the gray rather than trying to cover it entirely.
Mix the hair dye as directed by the box. You can choose a bottle specifically designed to highlight or use a straight hair dye. If you have long hair, consider using the regular dye so you have enough to cover all of the highlights you want.
Put on your gloves to protect your hands from the dye.
Part your hair as normal. You will want to begin with the area around the face and at your part.
Pick up a small portion of your hair and cover it with the dye. Saturate the hair, using the comb to work the dye through the section.
Wrap the now-wet piece of hair in foil to keep it from touching the rest of your hair.
Work your way around your face and down your part, alternating between sections of hair with dye and without.
Clip or bind the foil pieces together by section in order to get to the hair below. This helps keep it out of the way.
Repeat the steps with the next layer of hair. With each lower layer, do fewer highlighted sections to keep the look natural. Your hair gets highlighted more on top than bottom.