Here's a breakdown:
* Dark Hair (Browns, Blacks): These shades almost universally have red, orange, or yellow undertones. This is due to the pigments present in hair: eumelanin (brown/black) and pheomelanin (red/yellow). The amount and ratio of these pigments determine the hair's overall color. Even black hair has red undertones that become visible when light hits it or when it's lightened.
* Blonde Hair: Lighter blondes often lack prominent red undertones, especially cooler ash blondes. However, even some blondes can have golden or reddish hues.
* Red Hair: Obviously, red hair is dominated by red undertones, thanks to a high concentration of pheomelanin.
* Artificial Hair Colors: Artificial hair dyes are designed to deposit specific pigments, so undertones depend entirely on the formulation of the dye. For example, a cool-toned brown dye is created with blue/green undertones to counteract the natural red undertones in the hair.
* Why Red Undertones Matter: The presence of red undertones in hair is what causes hair to turn brassy when lightening the hair.
In summary:
* If your hair is a dark brown, dark blonde, or black, it almost certainly has red, orange, or yellow undertones.
* Lighter blondes *may* have red or yellow undertones, but it's less pronounced.
* Red hair is, well, red!
* Artificial hair color undertones are dictated by the product and the undertones are specifically used to create a desired hair color or to counteract unwanted tones that may arise when dyeing hair.
So, while not *all* hair colors have red undertones, it's a very common phenomenon, especially in darker shades. It's important to consider undertones when coloring your hair to achieve the desired result and avoid unwanted brassiness.