18.6Dorian

Start on D using C-major notes:

D E F G A B C D

Compare D natural minor:

D E F G A B♭ C D

Dorian has:

B natural instead of B♭

Formula:

1 2 ♭3 4 5 6 ♭7

So Dorian is:

minor, but with a natural 6.

That natural 6 is its characteristic color.