Here in the land that is base for HBO's Game of Thrones the talk of a Red, White and Blue Brexit as first described by Theresa May and increasingly mentioned by others since is not universally going down well. Let me explain why (in the language that GoT fans will find familiar).
Queen Arlene, First of Her Name surveys her Kingdom of the North from her White Keep (Parliament Buildings, Stormont). She was very much in favour of Brexit and her sigil is St. Edward's Crown on a background of Red, White and Blue. However, outside the gates of the keep the people however are not as much in agreement of Brexit as Arlene and her small (well not so small) council.
Prince Martin is meant to be a co-regent with Queen Arlene. His house's ancient sigil was an armalite and a ballot box on a background of Green, White and Gold, but now it is just the ballot box though some banners still show a shadowy figure of the armalite. He is opposed to Brexit and the mention of it as being Red, White and Blue is not going down well with his bannermen who largely were also opposed to Brexit.
Meanwhile in Kings Landing, Queen Theresa, First of Her Name, Queen of the Four Kingdoms and her small council have largely ignored that the Kingdom of the North has a large border with Europeros with which her four Kingdoms are looking to depart. There are many workers from the southern part of the island that the Kingdom of the North shares with Europeros. There leader King Michael, First of his name, also known by some as the Imp, or Leprechaun because of his diminutive stature and his hand Enda are very much in favour of Europeros are a little offended that Queen Theresa is asking them to control movement of Europeros citizens entering their territory as they have not signed up for Brexit but have signed up for the freedom of movement of Europeros citizens both into and out of their nation.
There has been a peace in the Kingdom of the North for only 3 decades and even then at times it has been tense. Talking up Brexit as being an issue that is Red, White and Blue may stir up some of the sleeping armies of the old days. Continuing to wrap this argument is patriotism based on symbols which still cause dispute in the Kingdom of the North contravenes the treaty that the Kingdom of the North was allowed a degree of autonomy over its own affairs. It is a part of the Four Kingdoms that allows civilians to follow in the Red, White and Blue sigil, or the Green, White and Gold one, or both if they chose too. Fealty is not a black and white matter, nor should it be hyped up in full colour.
Be warned those in Kingslanding (Westminster in this tale) not all the people of the Four Kingdom (United Kingdom) want to hear talk of Red, White and Blue Brexit. Here in the Kingdom of the North (Northern Ireland) some of us have been campaigned for safe and open spaces where everyone can gather. Your painting of Brexit as being a matter of Red, White and Blue while talking to little Englanders, is not so great to the fringes Northern Ireland and indeed Scotland.