You are quite right. If you don’t have grey hair, there is no reason for you to use permanent colour. A colour "rinse" (Demi-Permanent Colour) is a great way to get shine in the hair. When we colour our hair with permanent colour, we lose our natural pigment, so that there is space for the new colour to go within the hair. But your hair will never be the original colour again, unless it grows out. That is why when colour fades, it will always look red, orange or yellow depending on how light or dark you were.
A demi-permanent colour’s molecules sit on the outside of the hair, and do not change your original haircolour, they just wash out. But if your hair is not in a good condition, the colour could absorb into the hair, and become more permanent.
My salon uses REDKEN Shades EQ, which is the only demi permanent colour on the market that does not change your original hair colour at all and completely washes out back to your original colour. It also has a treatment built into it, so the hair is left silky and shiny and healthy. You even get a Clear Gloss that gives your current hair colour the amazing shine you would get from a colour, but without the colour!
If you are going to becolouring your hair at home, always read ingredients and make sure not to use a colour that has 20 or 30 volume peroxide as that automatically makes it permanent.
Hope this helps!
MIRRORS hair lab.