Wowza!

some say you arent a gardener.. until you have 100 pots to plant in fall ... there is no reason to plant ... at the wrong time .. it was near 100 yesterday in my MI ... it would have been foolish to plant ... im not sure the PNW has such days ... and if they did.. those peeps would probably be forced to take off their windbreakers ... lol ... if you want to hold them over.. place pots in shade... to keep the pot itself out of sun.. and water them when they need it ... basically no hot roots ... if you want to gamble.. go for it... if you have a few days of clouds and lower night temps.. jam them in ... you make it sounds like its today or never.. you really have so many timing options i dont know why you would waste effort ... doing it precisely at the wrong moment in time .... ken

Hydrangea macrophylla and serrata produce blooms that are color sensitive based on (a) the availability of aluminum and (b) the soil ph. When the soil is acidic and contains aluminum, the roots can absorb the aluminum and produce blue blooms. Your pink blooms were originally pink due to the soil pH being alkaline and-or the absence of aluminum in the original potting soil. Once the roots started growing into your garden soil with aluminum, they now turn blue instead of pink. My soil is normally alkaline so I get pink blooms by default. To get blues or purples, I simulate acidic soil by amending the soil to acidify it (a soil test done years ago indicated that the soil had aluminum). Macrophylla/serrata blooms typically go through a series of color changes as the blooms age and the color changes depend on the variety and type of hydrangea. One example, a new bloom may start pink and remain so for several weeks/month. Then the bloom may add shades of pink/reds/purples and remain so for several weeks/month. Then the blooms may add shades of green splotches and remain that way for several more weeks/month. Finally, the blooms turn all brown. If the blooms prematurely turn brown instead of going through similar color changes, it is possible that the plant is not getting as much water as it needs during the summer months or is getting too much sunlight. The blooms will eventually fall in 2022 on their own... at about the time when the plant produced the blooms this year or before then. Alternatively, you can deadhead now: cut the small petiole string that connects the blooms to the stems. The leaves should still look fine (until the plant goes dormant in the fall), provided that you are still watering well to maintain the soil as evenly moist as you can; maintain 2-4" of organic mulch (no rocks) around the plant up to the drip line or past it.

Interesting you mention size @Tim Wood as the ES website lists the size of SC as being much less than "full sized" i.e. less than 3 feet by 3 feet (which is reasonably comparable to WBG). https://endlesssummerblooms.com/product/summer-crush-bigleaf-hydrangea/ (It was because of its compact size that I planted SC "permanently" in a container last season)