Sometimes getting in to do a base color plus full set of highlights can be a serious time commitment. What I like to do to get the grey covered and freshen up highlights, is what Brambila Salon calls their "coastal".
It's a quick root touch up around the crown and just a couple quick foils to add a little dimension around the face.
Finished off by a killer blow out and I'm set on my color needs for at least 2-3 more weeks. Takes an hour tops and super easy on the budget ;-)