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?
Hair color product web sites offer the entire range of hair color available with them and what can be done with it. However, do remember that they are using professional models (with amazing skin) and you would need to discount some of the ideas that they demonstrate. The official web site however, does help you get the right shade and that is very important before you decide your hair color.