Shades EQ question

I have a question about the Shades EQ line.  My friend wants me to do a color re-touch to her hair and to use Shades EQ.  She has been going to a salon, and has about 2 inches of re-growth now.  Is there anything I need to know about Shades before I match up her roots to the previous color and go for it?  Any suggestions would be appreciated!!!