Hi,
My hair is naturally very dark brown, with a year old balayage and quite a few scattered greys, which are also quite wirey (nice!) , sits just above bra strap, so quite long, reasonably thick/coarse/frizzy/wavy - curly. Thank goodness for my Airwrap!!
My options are (unless you have another suggestion) blend out the grey with a permanent colour matching my natural and refresh the balayage, although my hair is a bit fried and frazzled, so not sure that's completely sensible 
or get rid of the balayage and have an all over permanent, maybe with more of a mahogany tone. I would rather have a semi, as I don't like using permanent these days. I've lost quite a bit of hair over the past few years and I'm not sure if this has played a part. Plus permanent can look a bit flat and dare I say, witchy? A semi probably won't touch the grey though, so probably not an option.
If I could get away with covering the grey with the highlights/balayage, I'd rather do that, but don't want to end up with that stripey look of the 90's highlights.
My skin tone is neutral, but more on the cool end I'd say. I'm 37 and don't really suit dark dark hair anymore. Very aging I think.
Anyway, enough ramblings - any suggestions would be hugely appreciated!
TIA