I started off using different colors because I liked them. Turns out that my brain really likes this style of information organization, and it's helped me a bunch when it comes to learning and sticking with good design habits!
Notebook: Colorverse Nebula
Pens, L-R: Platinum Preppy (fine, Colorverse Brane), TWSBI Eco (broad, Birmingham Pen Co. Lightning Twinkle), Opus88 Mini (fine, Pilot Iroshizuku Yama-budo), and Bonecrusher (medium, Diamine Writers Blood)
Photo description: Stationery items on top of a large desk mat printed with a night forest scene. A Colorverse Nebula notebook is open to two pages of notes and drawings on tips for designing snap-fit joints on 3d printed objects, written in different ink colors. The notebook is surrounded by pencils (a Bic mechanical and Tombow 4H), a plastic pencil sharpener, and a test tube rack holding four fountain pens.
There is something that tickles me about seeing a tool that makes 1D lines on a 2D piece of paper about 3D modelling.