[anononaut]

I use a multipen, a pen with multiple ink cartridges that can switch on the fly. Just like the one you had as a kid! I use four colors plus black for my day-to-day engineering journal. I use the colors for semantic highlighting. By default, I write in black. People, teams, and customers are in blue. I also annotate some things with blue arrows and words. Dates and very important notes are in red. Projects and tickets are in green. Meetings are in purple (with blue attendees).

I also do some clever things like separating days with black lines and a little box for the date, but the first day of the week is red so I can easily see week boundaries. As a whole, it makes scanning for what I'm looking for very easy. Since I usually know at least what meeting a decision was made in. Or if I'm looking for my notes about a teammate, that's another color. I've been doing this for four years and have really refined my process.

My pen of choice is a Coleto 5-color multipen. They are a pretty cheap plastic and I'm not in love with it. It's just the best I've used with five colors. For ink cartridges I use Pilot Hi-Tec-C, 0.4 mm. I highly recommend it, but start with a day book to see if it's useful to you first.

[quercusa]

I remember getting a Bic 4-color pen as a kid - it was very exciting.

[jerlam]

Multipens are very underrated, especially when they're all using the same new technologies as the better gel and ballpoint pens.