Dying over highlights is a very challenging task with many things to consider. Often, several different coloured dyes are used to achieve a look of an entire head of hair appearing one solid colour. When dying over highlights, the highlights absorb colour much easier than the rest of your hair, which makes it difficult to rid your hair of multiple colour tones.
Consider making an appointment with a professional colourist. Dying over highlights to achieve hair with one even tone is a very difficult task. Professional results will be hard to achieve on your own unless you've had previous experience with colour matching. Most likely, you will leave the salon the same day with perfect colour over your highlights. Going to a colourist will be much more convenient and less time consuming.
Establish the overall colour you are trying to achieve. If you decide to attempt this task on your own, you first need to decide what colour you'd like your hair to turn out. Keep in mind that it is much easier to dye over highlights using darker-coloured dyes. Lighter colours have a very broad colour range possibility. This makes colour matching much harder when dealing with multiple shades of hair. Darker colours have a much smaller range of colour results.
Match dye colours accordingly. You will need to attain two different-coloured dyes. First, you need your primary colour. Your primary colour is the dye that will be covering the majority of your hair, with the exception of your highlighted areas. This colour will resemble the final desired hair tone. Second, you need a secondary colour to reverse your highlights and make them appear the same colour as the rest of your hair. This means choosing a colour with the capability of the same tone as your primary colour when applied over highlights.
Refer to your primary colour in order to properly establish a secondary colour. The primary colour you have chosen is the basis of your decision because you want to choose a secondary tone that has the capability of matching your primary tone perfectly when applied over highlights. Make sure your secondary colour is the same colour tone as your primary colour. For instance, if your primary colour is an auburn brown you want to stick to different shades of brown with a red tint as well. In most cases, your secondary colour should be two to three shades darker than your primary colour.
Separate your hair. It is important that you dye your highlighted hair separately from the rest of your hair. Section off the highlighted areas of your hair using hair clips. To ensure that you don't accidentally apply primary colour to your highlights, it is recommended that you wrap your highlighted hair in tin foil.
Apply the primary hair colour. Dye all of the hair present outside of the sectioned highlights. Apply even amounts of your primary hair colour choice throughout your hair and let it sit for approximately 20 to 25 minutes. Once you have let the primary colour sit, remove all hair clips and tin foil so that you can thoroughly rinse your hair. Towel dry your hair and brush out any knots or tangles.
Apply the secondary hair colour to your highlights. To do this, you will need to use tinfoil once again in order to contain the highlighted hair within the tinfoil, as to not disrupt the rest of your hair with secondary colour. Place a piece of tinfoil under a strip of highlighted hair and apply secondary colour along the entire strands of the highlighted section. Gather the section of highlighted hair within the tinfoil and carefully fold the foil in half to ensure the dye stays in place. Once you have applied secondary colour to all of your highlighted areas, check on the colour every five minutes. Dye processes very quickly on light hair. It is important that you check back often to see when the colour has reached its appropriate potential. You may need to leave the secondary dye to sit anywhere from 10 to 30 minutes. Once your highlights have processed to the appropriate colour, rinse your hair thoroughly once again.
Do not use temporary dye when colouring over highlights. When using more than one colour of dye, always use the same brand.
If you are attempting to dye over highlights yourself, refrain from using ash colours, as the result may be a greenish tint where the highlights used to be. Do not leave dye in your hair longer than 45 minutes.