Alicent’s green dress is a major turning point in House of the Dragon

polygon.com:

House of the Dragon’s fifth episode is an eventful one. But between the weddings, feasts, and fights, the single most important moment was when all eyes were on Alicent Hightower’s dress.

While the show itself gave a small explanation of its historical significance, it plays an important enough part in the rest of the series’ story. So let’s talk a little bit more about Westeros’ most famous green dress.

[Ed. note: This story contains spoilers for House of the Dragon episode 5.]

Essentially, everything in House of the Dragon through episode 5 has been leading up to Alicent walking into Rhaenyra’s wedding wearing a dress of bright green. While the late arrival of the queen was noticed by all, it fell to Larys Strong, perhaps House of the Dragon’s cleverest character, to clue the audience into why the dress’ shade actually matters.

First of all, green is about as far as you could get from the traditional black and red colors of House Targaryen, symbolizing a lack of support for the family — and Rhaenyra — by the queen. More important, as Larys explains, the light at the top of the Hightower in Old Town (the seat of Alicent’s family and the building that gives them their name) glows green as a symbol for war, a bit of information added to the show that wasn’t present its source material, George R.R. Martin’s Fire & Blood.

In other words, Alicent’s perceived betrayal of trust from Rhaenyra and her husband King Viserys, which also drove her father, Otto, from King’s Landing and his position as Hand of the King, was severe enough for Alicent to functionally declare war on House Targaryen. As her first real act of self-agency, Alicent has chosen to end the uneasy — and always unequal in one direction or the other — friendship