Almost all the typewriters I have used have had a red and black ribbon but I never finding myself using the red for much and it never seemed to have a whole lot of utility despite the red and black being so iconic..
Was there some common use for red in the past and what do you use red (or green or blue) for?
What LvG says, of course, and also playful, eye-catching announcement posters. Today I often write light-hearted letters in red, as much to use up the red and save the black as to get attention. HTH
Of course you could use the second color of your ribbon to add some design to your documents. I use my black/blue ribbon for this, as blue is less alarming than red.
