Hydrangea blooms change as the blooms mature. Blues require a certain level of acidity and a certain amount of aluminum & other minetals. Moisture, root development and the weather can also influence the color. As any or all of these things change, the shade of color may change. Sometimes the change takes a few weeks to a month. New shrubs may vary more than usual but should "settle down" colorwise as the plant becomes established. Soon you will notice the presence of greens and pinks before the bloom browns out.

Interesting. I've seen blue and pink just never this violet.

If the hy was blue when you bought it .. It's a good chance come next yr , when it roots start to grow in the new soil you'll have a Pink hyd ...I would think most Macs in Z8b would be Pink?

It is part of the colors you might see from blue to purple to pink.

Pink requires alkaline soil (or a lack of aluminum) and is not zone dependent. In Georgia's zones 8a and b, for example, the blooms tend to be blue due to acidic clay soil.

Thank you Luis, didn't know that about Georgia soil...I assume wrong

Generally speaking, the blooms nearly always "darken" as they fill out. So the initial color is only a "hint" of what the final one will be.