Highlights & Sun Exposure
A: For general highlighting, the biggest risk you run from sun exposure afterward is the potential that the sun will further lighten the hair, either blurring the difference in your base and highlight tones or simply lightening your highlights even more than you intended.
Prolonged or repeated sun exposure after a color service can result in some fading of the red color, and leave a brassy look. This can also happen as a result of exposure to chlorine in swimming pools and frequent heat styling. Basically, any process that swells the hair shaft and opens the cuticle layer can result in a more rapid loss of the red pigment.
Sun exposure does this. The heat of the sunrays penetrates the hair shaft and causes the hair to swell slightly (depending on its starting condition) which raises the cuticle layer. The color molecules that were deposited in your color service are then dispersed by the sunlight's UV rays, or are more readily affected by water and other substances that come in contact with the hair.
This can also happen with natural hair colors, too. I'm sure we all know people – maybe even ourselves – who have a "sun-kissed" look to our hair during the summer months. The effect varies from person to person, but it definitely happens.
My advice is to use a color boosting shampoo and conditioner for all over color to keep your color looking fresh, and to get and use a conditioning product with a sunscreen for use on your hair when you are going to be outside if you have tinted highlights. The sunscreen will protect the hair from the harmful effects of UV radiation and ensure that your color lasts as long as possible.
©Hairfinder.com
See also:
Fading red hair
The effect of the sun on our hair