What is the Difference: Home Color vs Salon Color

Over the counter color is normally a liquid formulation, which requires a large color molecule. In order to penetrate the hair shaft & get through all the 7 to 12 cuticle layers- the hair shaft must be opened wide enough to admit the color molecule into the interior of the hair. This is accomplished by using more ammonia to open the cuticle layer wide enough to accept the large molecule, & this is where over the counter color can cause damage.
Most clients color their hair once a month, it they are gray or 6 times a year if they are pigmented. Pulling the formula through each time as a refresher to the hair equates to putting ammonia over ammonia each & every time!
Ammonia is the culprit, & eventually it will leave the hair rough in texture, the color will fade out sooner & the hair will lack shine. Salon color has much smaller molecules, uses less ammonia, has 100% oxidative dyes with no direct dyes & works off of a 20 volume peroxide system, which is all healthier for the hair.
In conclusion hair is healthier & shinier. Salon professionals have the ability to refresh the hair with a demi-permanent that doesn't contain ammonia, so the hair shaft only gets one application of an ammoniated product.