Those are actually YELLOW dog Democrats (idiots in the south who blindly support RATs no matter what because "my daddy was a Democrat and his daddy was a Democrat and his daddy was a..." They are a dying breed, thankfully. (Although I think even few neo-confederates on this forum who despise Republicans and sing the praises of how great things were under RAT rule are closet yellow dog types)
Blue-dog Democrats are allegedly "conservative" RATs who claim they break ranks with their party over major issues. Of course, most of the "blue dog Democrats" around in the 21st century just claim to be "conservative" and "independent of my party" to get elected, and then vote for horrible socialist crap like Obamacare without blinking an eye.
The article is correct that the "blue vs. red" color scheme works the opposite of the way the media defined the colors in the United States. For example, the Canadian equivalent of the term "RINOs" are "Red Tories", because they're phony conservatives who support marxist legislation. "Blue Dog Democrat" is a pre-2000 example of the correct color terminology. Back in the 50s, if you claimed a Republican was "Red", everyone knew what it meant, and it was an allegation he was a closet leftist.
One oddly, Crook County Illinois has primary ballots colored by party, and the GOP has always been assigned yellow, why the RATs have always been assigned green (not suprisingly, there are 10X as many green ballots on election day thanks to the zombies in Chicago). The Green Party had "qualified" ballot access from 2008-2012, and I believe they used pink for them.