The division between "red" and "blue" states in the united states refers to:

The correct answer is - Republicans and Democrats.

When we see a map of the United States with the colors red and blue, than it usually means division of the country's states by political orientation. The red color refers to the Republicans, while the blue color refers to the Democrats.

In general, the Republicans enjoy more support in the states of the southern half of the country, while the Democrats enjoy more support in the northern half of the country, with the occasional exception of course.