Wilkerson Mill is excellent - big plant for not a lot of money - you won't get the pot though which is kind of weird in a way. Hirt's on eBay has very small starter plants but then you get what you pay for - wished I had babied what I got from there - most died just putting them in the garden. I was pleased with Bluestone until last year - kind of small last year so I didn't order a thing this year.

Joy Creek in Oregon sells/ships great hydrangeas. What zone are you in, can you grow h. macrophylla there without winter protection and still have blooms? The listed climate range for hydrangea can sometimes mean the plant itself, not the flower buds....and not helpful if your goal was flowers.

Hydrangeasplus.com, Wilkerson (hydrangea.com) and Joy Creek (joycreek.com)are all very good choices IMHO. You can also order Proven Winners Hydrangeas directly from that wholesaler at www.provenwinners.com.

Regarding color choices, colors in non-white H. macrophylla, serrata and a few others are a function of soil acidity and the amounts of aluminum in the soil.

Joy Creek is a favorite of mine. If possible choose a company that is close to you or in the same growing zone. Being able to speak to a real person from the nursery for questions or suggestions is a great bonus. Check their return policies. But the eventual colors of your plants may be different from the photos in the catalog or website as Luis suggests. It helps if you know if you know the acidity of your soil.