Paniculata's tend to go a bit pink as they fade.

Paniculatas produce white flowers. They often go through a series of colors - most hydrangeas do - as they pass through the season and like many white flowers, they take on pink tones as they age. It has nothing to do with soil conditions.

Some paniculatas are bred to develop the pink coloring early or more intensely - like 'Pinky Winky' or 'Quick Fire'.

If you do not have sufficiently acidic soil with appropriate levels of aluminum (what develops the blue color in Hydrangea macrophylla), 'blue' flowered hydrangeas will tend to the pink or muddy purple tones. And since soil pH is difficult to change permanently or to any significant degree, you will have to keep working on maintaining the appropriate pH level. It is not a one-time shot. Irrigation water will also have an impact. Much of the water supply in SoCal is alkaline and unless treated, will "pink out" your blue hydrangeas.

I am in san francisco, but I think my water is super alkaline, but other people around here have blue hydrangeas, so it can be done. I just never did it. I do remember now that I heard little lamb can turn pink in the end of the bloom cycle, I just did not think it would be that pink. That photos is really pink, almost red in parts.

Never trust the photos in catalogs, either print or online, to be all that accurate. Go to a nursery or better yet, a garden, to see the plants in person, for a true representation of what the plant looks like, and how it might perform, in your area.