Paige orbs the crystal through a clear pane of glass to her left. Later in the same scene, the hole left by the crystal is in a pink-tinted window on Paige's right.
When Paige orbs the pint of ice cream with three spoons in the beginning, the ice cream has the lid on it. After they cut to Phoebe very briefly, they cut back to Paige and the ice cream is now open and Paige is taking a bite of the ice cream. There is not enough time for this to happen in the amount of time between showing Paige, then Phoebe and then Paige again.
A "blue moon" is not actually the color blue. A blue moon is an additional full moon that appears in a subdivision of a year: either the third of four full moons in a season, or a second full moon in a month of the common calendar.
When the charmed ones look out of the window at Magic School, you can see the city of San Francisco under the blue moon. Magic school is located in another realm entirely, not in San Francisco or any other city.
When the demon-possessed Leo attacks Piper in the attic, the windows behind him show a daytime view in one pane, and a night-time view in the pane next to it.