Context: Philippine flag is the only national flag in the world that has an official war variant. If the red side is up, it means we are at war. This only happened in history two times; during the Filipino-American War, and World War 2.
There are a few codes for US flags.
Upside down = distress
Grayed out = mourning
Blacked out = Defiance or “no surrender”. Or no prisoners will be taken, no surrender will be given. Note, only the first has any official recognition