Colorful Second Brain - Part 1: Crafting your colors in Excalidraw-Obsidian

Color choice is the difference between a second brain that clarifies ideas and one that overwhelms them—and Excalidraw’s color system in Obsidian is flexible enough to support both. The session lays out practical ways to control fill, stroke, opacity, and color formats, then shows how to reuse styles and automate color changes with Excalidraw-Obsidian scripts. The payoff is a workflow where colors aren’t guesswork: they’re specified, copied, mixed, and batch-adjusted.

The walkthrough starts with element-level controls. A rectangle’s fill and border (“background” vs “stroke”) can be set independently, but transparency behaves differently for each: setting the fill to transparent works, while stroke requires entering “transparent” manually in the edit box. Opacity is then demonstrated as a spectrum—fully transparent on one end, fully opaque on the other—and the consequences of semi-transparent strokes become clear when overlapping elements: a “black” border can appear gray because the stroke itself is semi-transparent.

Dark mode introduces another critical detail: colors invert. A stroke labeled “black” renders as white, and a “white” fill requires typing the opposite value because the system flips the palette. That inversion can feel confusing at first, but the session frames it as a predictable rule once you know to mentally swap light and dark.

Next comes color representation. Excalidraw accepts multiple formats: HTML color names (like “dark green”), hexadecimal, RGB, and HSL. Hex and RGB are tied to the same underlying mixing model—RGB uses three values (0–255) for red, green, and blue, with 255 mapping to “ff” in hex. HSL shifts the mental model to a wheel: hue is an angle (0–366 degrees), saturation controls vibrancy (0% becomes gray), and lightness moves from black (0%) through mid-range (50%) to white (100%). Opacity can be added across formats: an extra alpha value for RGB/hex, and a final alpha number for HSL (0 meaning transparent, 1 meaning fully opaque).

To avoid typing numbers, the session recommends two color-picking routes: copy/paste from an online color picker, or use an OS-level picker (PowerToys on Windows, Digital Color Meter on macOS). It also highlights Excalidraw’s style transfer: right-click an object, copy its style, then paste it onto another object to replicate fill and stroke settings quickly.

Finally, the session moves from manual control to automation. Using the Excalidraw script engine scripts in Obsidian, it demonstrates changing fill styles (including zigzag and dots, with a performance warning for large dotted shapes), adjusting background opacity without forcing the stroke to change, and batch operations like darkening/lightening backgrounds via HSL lightness adjustments. A special trick targets “open” shapes: convert a free-drawn object into line form, apply background color using a shadow/clone-based script, then ungroup to reveal a colorable background layer. The session closes by previewing future episodes focused on choosing palettes, switching them on the fly, and applying consistent coloring across an Obsidian “world” (headings, callouts, highlights).