Red is the left-most, initially already selected, default colour option.
But is it a correct assumption to imagine that 90%+ of players chose to paint their Bellhart home red?

I'm guilty as charged at least. Because Hornet = Red.
I considered Black or Orange though. But the latter felt like it'd bleed in way too much with the broader colour scheme of Bellhart. And with Black I was worried my home would perhaps end up looking a tad burnt maybe. So Red it was.