To begin with the choice of colors would top the list. So what family of colors is on your mane wish list? Are you looking to alter the color or color the gray?
Seems those that bring you hair color in a box have gotten the message. You'll notice more fruity scents rather than something that smells like a toxic waste dump when using them. Apparently all part of an effort to make the time spent coloring your hair seem more like putting on make_up rather than doing something that requires you don a hazmat suit.