I have naturally auburn hair that started going grey around my 30th bday.
My stylist uses Framesi color glaze on my hair since it's only about 10% grey... trying to avoid the damage of real dye. Red hair is a pain to maintain but I use this after about 3-4 week mark in conjunction w Aveda Madder Root Conditioner... and it does a great job of disguising the greys peeking through.
I'd leave it on for 3 minutes or so. Also, I have dry coarse hair so I only wash my hair every 3-4 days so maybe that's why it helps? Not sure if it's an everyday shampoo for you oily hair girls.