Banners !!LOTS OF SPOILERS!! if you haven't read the books!!!!!!

So we know that the Greens won. They had a green and yellow banner, but we see dany adopts the traditional red and black banner. So when did they change from the green back to the red and black banner? Presumably Dany knows that as her house banner and she got that info probably from her brother who would of seen it maybe? Idk what do you think?