The first thing that came into my mind is the 4-colour pallpoint pen from Wedo: https://wedo.de/4_colour_ballpoint_pen_chrome https://wedo.de/4_colour_ballpoint

The first thing that came into my mind is the 4-colour pallpoint pen from Wedo: https://wedo.de/4_colour_ballpoint_pen_chrome https://wedo.de/4_colour_ballpoint_pen_chrome It is very practical if you want to use different colours for note-taking away from your desk. I had my first one aprox. 40 years ago when I was a school boy. Its design hasn't changed since.