* The underlying color of the highlights:
* Light Blonde Highlights: If your highlights are very light blonde, the red dye will likely take well and result in a vibrant, true red.
* Darker Blonde or Bronde Highlights: The red might not be as bright. It could result in a more auburn, reddish-brown, or copper tone.
* Brassy Highlights: The red could emphasize the brassiness, resulting in a warm, reddish-orange tone. It's best to neutralize the brass with a toner before applying red dye.
* The type of red dye:
* Permanent: Will provide the most lasting and vibrant color, but also requires the most commitment and can cause the most damage.
* Demi-Permanent: Less damaging than permanent dye, lasts around 24-28 washes. Good for trying out red or adding a red tint.
* Semi-Permanent: Least damaging, deposits color without lifting, washes out the quickest (around 6-8 washes). Ideal for experimenting or refreshing red tones.
* Red Toner: Specifically formulated to deposit red pigments to brassy or blonde hair.
* Porosity of the hair: Porous hair absorbs color quickly, which could lead to a more intense result.
Here's a breakdown of possible outcomes:
* Even Color: The dye might cover the highlights completely, resulting in a uniform red color. This is more likely with darker shades of red and/or light highlights.
* Varied Tones: The highlights might take the dye differently than the rest of your hair, creating subtle variations in the red tone. This can add dimension.
* Uneven Color: If the highlights are drastically different in tone or your hair has varying porosity, you could end up with an uneven color distribution.
* Red Highlights: If your base hair is dark, you might end up with red highlights instead of an all-over red.
* Brassy/Orange Tones: If your highlights were brassy, applying red could amplify those warm tones, leading to an undesirable orange or reddish-orange color.
Recommendations:
* Strand Test: Always do a strand test on a hidden section of your hair (preferably a highlighted strand) before applying the dye to your entire head. This will allow you to see how the color will turn out.
* Consider a Color Filler: If your highlights are very light and you're going for a darker red, consider using a color filler first. This will add underlying pigments to help the red adhere better and prevent it from turning muddy.
* Talk to a Professional: If you're unsure about the best approach, consult a professional colorist. They can assess your hair's condition and recommend the right products and techniques to achieve your desired red hair color.
* Neutralize Brassiness: If your highlights are brassy, use a blue or violet toning shampoo/mask before applying the red dye to neutralize unwanted warm tones.
In summary, putting red dye over highlights can be successful, but it's essential to consider the factors mentioned above and take precautions to ensure a desirable outcome.