Crazy theorycrafting time, but I believe I have deduced the gala color(s) for PCGF (at least for NA).
Premises:
1) GungHo is currently releasing the Jewel Princesses series.
2) The current biweekly features skillups for the Jewel Princesses.
3) The dark Jewel Princess's skillup (gadget) was released in the dungeon before the princess herself was releases, thus the order of release has is already predetermined.
4) According to PADX, the other biweeklies in this series also feature the skillups for the other Jewel Princesses in the same pattern.
5) According to GungHo's EU Facebook page, the next gala is Water, on the 20th - 26th.
6) Galas shift colors on Fridays.
7) PCGF is historically the end of May Godfest.
Assertions:
1) GungHo is releasing Jewel Princesses in the order of the biweeklies. As per the name of the current biweekly, Fire was first, and Dark was second.
2) Per GungHo's EU Facebook page, as the next gala is Water. Per PADX, this means that the next biweekly must be Water and Light Metallic Star Dragons.
3) Therefore, the gala after Water must be Light.
4) Light Gala would run from the 27th to the 2nd, given the Friday weekly pattern.
5) The only remaining Jewel Princess would be the Wood gala one, which would start on the 3rd.
The 64 million magic stone question is when is PCGF precisely. If I were GungHo, I would hold it on the 2nd and 3rd: Day 1 - light gala, Day 2 - wood gala to maximize rolling for specific Jewel Princesses.
I've thought way too much on this, lol.