For those wondering why I wanted to know whether the Moon was blue or purple, earlier, it's due to how Yasu apparently can't see one of them:
Assuming the Moons and their colors represent people, then since Yasu can see Maya:
She can presumably see the Green Moon.
Since Yasu can see Ayane:
She can presumably see the Blue Moon.
However, Yasu can't actually see Sekai:
So, she presumably can't see the Red Moon.
Those colors seemingly belonging to those characters in particular (Ami is actually Pink apparently, based off the color of their names in game). This would also support theories that these Moons are related to those people in the first place. So far, Sekai is the only thing Yasu notably can't see, besides that Moon, as far as I recall.
Of course, Yasu might also just be incapable of seeing "Red", because it's "bad":
And if that Moon is actually purple, then it seems less notable that Yasu was shown seeing and not seeing these 3 characters in one Beach update, then mentioning seeing and not seeing those 3 Moons in the Beach update afterwards.
Anyway, at this point I'm leaning towards Yasu being unable to see the Red Moon. Why this matters, I do not know.
Also just for something to think about, apparently Ami's and Ayane's colors represent Springtime to Yasu:
Which seems interesting.