I'm having the same exact problem this year with my container-grown hydrangeas down here in South Texas and was also wondering what was going on. Earlier this year my hydrangeas were gorgeous and now the blooms are as green as the vegetation.
But I think I found my answer this morning when I read a thread where [url=https://www.helpfulgardener.com/forum/viewtopic.php?t=9417&sid=2a5cdedc4638facd178dac4b4585c3f8]fhj52 posted[/url]:
"Echinacea prefer slightly acidic soil so it is possible that the color variation is from the alkaline soil. <snip>
No method is permanent but sulfur will last longer.
After reading this post I realized my husband had sprayed our yard several times in ?late fall/early spring? with a sulphur wettable powder mixture for a flea problem we were having. I'm betting that's why I had the beautiful pink and blue blooms I had.
Tomorrow I'm going to spray my plants with some sulphur mixture and see what happens!
"Our elders instruct us to always walk upon Mother Earth with respect, gentleness, and with thankful hearts. We must never deviate from the fundamental precept of stewardship, or we will be capable of causing great harm."