Just had a quick poke about and it appears I am right and the time between treatment and painting depends on how far the drying process has gone, but this explains it quite well and tells you how to test.I will have to look into the time-lag from "dip in preservative" to "able to take paint", I wasn't aware of that, but it makes sense.
I am not keen on the green/blue tint of the dip, but I know the timber fades to a silver-grey in time as you said.
Herself wants her Barn black, so Black it shall be (eventually).
But your Mrs doesn't need to worry, it won't be long, you may even be able to paint it quite quickly.
https://thehonestcarpenter.com/blog/can-you-paint-treated-wood/
I didn't watch the video, how to test it is further down in the text.
Best of luck with it!