Most of what Claude Code outputs is English. Tool output, permission prompts, reasoning traces, explanations — I tracked my actual screen time over a few sessions and the ratio held around 80% prose, 20% code blocks. Every terminal theme I had was built to make keywords and bracket pairs pop. None of them were built for reading paragraphs for four hours.
So I built klein-blue: four Terminal.app themes anchored in Yves Klein's IKB pigment, APCA-verified for body-size prose legibility, and mapped to the specific ANSI slots Claude Code actually uses for tool output and permission prompts.
The constraint that shaped everything: pure IKB fails as readable text on a dark ground — APCA Lc -12, effectively invisible. To keep the pigment present without making permission-prompt text unreadable, I split it across two slots. The ansi:blue slot gets pure IKB for decorative borders and highlights where legibility isn't load-bearing. The ansi:blueBright slot — which Claude Code routes permission-prompt text through — gets a lifted Klein-family value (near-periwinkle, Lc well above the body-prose gate) that stays readable at body size.
The four variations differ in how much brand color they absorb:
- Klein Void Refined — balanced, no dominant second color
-
Klein Void Sand & Sea — accepts Claude's
ansi:redBrightsand color as a second hero alongside the blue - Klein Void Prot — every accent passes strict APCA gates: body >= 90, subtle >= 75, muted >= 45, accent >= 60
- Klein Void Gallery — maximum void, one blue, everything else near-neutral
Prot is the only variation where every role is guaranteed to pass. The others make deliberate tradeoffs — aesthetic weight over strict compliance in the decorative slots.
The themes ship as .terminal profile files for macOS Terminal.app. One thing worth knowing before installing: Claude Code must be set to dark-ansi via the /theme picker, otherwise it ignores the ANSI palette entirely and falls back to its hardcoded RGB values.
git clone https://github.com/robertnowell/klein-void
cd klein-void
bash install.sh
restore.sh rolls back if something looks wrong. MIT licensed.
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