Is white the color for mourning? Why are they all wearing white?

Yes, thw white clothes are for mourning. The Crown Prince’s younger brother died.

Oh that's really suprising. In almost all of the cultures mourning color is black.

I don't know about other cultures but back in the day in Korean culture that's what they were when they were mourning I believe i saw it when I watched historical dramas

not all cultures obv.

In Hinduism and Budisim the mourning colour is white.