The type hydrangea that turns pink in alkaline soil, blue in acid soil, and purple in neutral soil is hydrangea macrophylla or French hydrangea. My grandmother had some beautiful blue ones that she grew in fairly deep shade on a fairly damp part of her yard. I haven't grown them myself in a long time, but they're sure beautiful. As long as they get plenty of water and not too much sun, they'll do fine.
I'm thinking about ordering hydrangea arborescens, one of our native types. I've tried h. quercifolia/oak leaf hydrangea, another native, but it didn't do well for me. There are some 'lace cap' hydrangeas that are really gorgeous, but I've never tried them.
By the way, frenchkitty, they changed the zone map back to the way it was up until the early 1980's with the coast being in Zone 9. I'm right on the border of zones 8 and 9, so, since we've had warmer than normal weather for the last few years, I went with Zone 9 - if this colder weather keeps up, maybe I'll go back to Zone 8. :)
MissSherry