Once she studies your hair, its condition, its style, its cut, and your lifestyle (e. g., how much time you plan on spending on your hair each day), she will then make some recommendations for color and maybe even a more suitable style for you. Plan on being there for a few hours.
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.