Here's a few thoughts....
This is more than one single plant - there is no single hydrangea that will bloom simultaneously red, white and blue.

Blue hydrangeas ARE influenced by soil pH, whites are not and pinks/reds are variable - some are, some aren't. At any rate, it is unlikely that you will get the same intensity of color of all three types in the same soil.

directgardening.com has an extremely poor rating on the Garden Watchdog, indicating that its plant quality or customer service or both are deficient. That this company should be somewhat suspect is evident in its statement that this hydrangea will be hardy in zones 3-8. Hydrangea macrophylla (which these plants are) are borderline hardy in zone 5 and generally require winter protection in that zone (and often in zone 6) to ensure flower bud development. With only a couple of exceptions - which these plants are not - it is highly unlikely to be root hardy in zones 3 & 4.

I'd take this with a very large grain of salt and save your money for a single hydrangea plant of your choice best suited for your location. In zone 7, you shouldn't be very limited in your choices :-)

It is rare, but not improbable, for Hydrangea macrophylla to have different colored flowers on the same plant root stock. A neighbor has one of the so-called tricolor Hydrangeas, but it has had only blue and pink flowers for the past 20 years. I don't know if it ever had any white blooms. I have a Madame Emile Mouillere that has white mops and blue lacecaps on the same plant, as it is planted in acidic soil. If the plant from directgardening turns out to be a dud, it's your loss. You will never obtain a replacement or refund from that shady operator or any of the other named companies operating from that Bloomington, IL location. I have been trying for 3 years to have them honor their warranty, without success. All printed terms of the warranty were complied with, but that doesn't seem to matter to them. Save your money and buy from an honest firm.
Rb

i think it is obvious from their text that the 3 different colors are on separate plants in the photo.
they say "one planting", not one plant.
by wording it that way, they are not lying, just misleading, perhaps.

Take a look at this site. They are most likely miss leading.

Gary

Here is a link that might be useful: Daves Garden

Take a look at this picture of Endless Summer. (Scroll down to the Alabama pic. It started blue but aged to pink, blue and a very pale pink that's almost white. I have heard that Forever and ever can have pink and blue on the same plant if soil conditions are just right.

Here is a link that might be useful: multicolered endless summer

Oooohhhh, how I wish I had read this thread before!!! I recieved an order from directgardening.com a week or so ago, including 10 "color changing" hydrangeas. I actually had posted in this forum, earlier this morning, about them. This was my second time ordering from this company. Last time I was slow in getting the plants in the ground and lost most, if not all, of them. Now, I am wondering if they would have survived anyway. In addition the the hydrangea, I ordered 12 barberries, 50 periwinkles, a kousa dogwood and a snowball bush. Wish me luck!!!