Hmm, they should turn pink. I would monitor the blooms to see if the tan parts progress to pink, green or what. I would be upset if they go from white to brown or tan to brown, both of which would mean that they dried out early.

Typically, not enough sun, too much heat/sun and lack of water (too much water) can cause color changes or can cause extended color changes (so the color lasts an unusually long time).

I saw some Incrediballs (H. arborescens) go from white to sandy color to pink-green at a local plant nursery. Obviously, those were not established like your 4-year old plant. Want to give the blooms -say- 3-4 more days of observation and post an update?

thanks for posting these pictures

i have noticed this as well

the color has a slight pinkish tent but some has a brownish pink

noticed this with both VS and one Bobo

i will observe it for few days and take a pictures

I notice that the grass in your photo looks fairly dry, so insufficient water may be an issue. Are the shrubs mulched? I would try next summer to give them a layer of mulch and if there hasn't been a reasonable amount of rain, give it a good soaking (s-l-o-w trickle from hose at base of shrub for an hour) at least every couple of weeks. Then see if they have nicer late bloom color. I don't know if starting this now will help the remaining white ones turn pink.

VS **does** do better with less sun. The one I have in 20-30% sun has larger blooms and they're more pink.

I will move it next year to a milder place. It is in sun all day now, facing south. And it has been hot this year.Maybe it will do better planted east or north.