Two parts Medium brown mixed with one part warm auburn will give a nice reddish brown color. For the reistant silver hair, make sure she applies the color full strength(equal parts color and developer) to the new growth and let it process with a cap for at least 45 minutes. whatever color is NOT mixed with the developer can be sealed and saved for the next month. Remember, once you mix color with developer, you have to use it immediately and you cannot save it.