I defined the Red Tribe as being "made up of the 23% of voters who are pro-UK Brexiters [mnemonic: red as the cross on the English flag]". Politically they're probably most like to identify with the Tories or with UKIP.
From a pro-independence point of view, it's the least interesting group because it's so unlikely any of them can be convinced to support Scottish independence, especially when it comes with the prospect continued EU membership.
It's worth noting that although they make up less than a quarter of Scottish voters, they have a majority south of the border (or at least they did at the time of the Brexit referendum). They also hold political power in the UK, and as the only tribe they have won two referendums in short order, which means they're feeling confident and bullish.
And yet – they can also be angry and touchy, because they were in a minority for so long on the question of Brexit, and they're fearful others will undo their achievements. Of course they hate the SNP leadership, who represents the polar opposite of their views.
The Red Tribe has won some temporary allies in the Yellow Tribe, who don't really want a new independence referendum before Brexit is done and dusted, and their relationship with the Green Tribe is now rather uneasy, because these pro-UK Remainers can suddenly see the attraction of Scottish independence within the EU.
It'll be interesting to see whether the Red Tribe decides to rebuild their relationship with the Green Tribe (for instance by opting for a softer Brexit) or whether they end up scaring them away by being far too extreme. Whether we get independence soon depends on the answer to this question.