Like yellow, orange is not a colour I generally associate with writing. I have, however, some correspondents who apply it fearlessly, and without loss of legibility. Orange is also, as a secondary colour, a bit of a conundrum; where does it officially pick up from yellow, and where is the hand-off to red?
Clicking the colour will take you to the maker’s page.
de Atramentis
Skrip
Herbin
Iroshizuku
Noodler’s