There is no "grey side". Grey Jedi = a Jedi who is considered to operate outside the [perceived] limitations of the Jedi Council's orders and such.
"There is something going on in time and space, and beyond time and space, which, whether we like it or not, spells duty." -Winston Churchill
"For of all sad words of tongue or pen, The saddest are these: 'It might have been!'" -John Whittier
"Apathy is death." -Kreia