Terminal themes tuned for prose legibility, not syntax highlighting

Source: Dev.to

Introduction

Most terminal themes are built around syntax highlighting — they optimize for keywords, strings, and operators. When your screen is 80 % tool output, reasoning chains, and permission prompts, that focus is the wrong target.

Klein‑Blue Themes

I built klein‑blue as four Terminal.app themes around Yves Klein’s IKB pigment (hex #002FA7). Each theme answers the same question: how should Claude’s sand brand color (ANSI redBright) behave in your terminal?

The Four Variations

• Klein Void Refined – balanced; IKB is the single accent, sand is neutralized so there’s no brand competition.
• Klein Void Sand & Sea – accepts sand as a second hero color; IKB and sand act as dual anchors.
• Klein Void Prot – the strict one; every accent role passes APCA Lc gates (body ≥ 90, subtle ≥ 75, accent ≥ 60).
• Klein Void Gallery – maximum void; one blue, everything else as near‑neutral as possible.

Contrast Problem with Pure IKB

Pure IKB fails the APCA contrast test as text on a dark background:

Lc: -12   (threshold for body text: Lc ≥ 90)

To solve this, the themes split IKB across two ANSI slots:

• ansi:blue – pure IKB for decorative borders and highlights (legibility not load‑bearing).
• ansi:blueBright – a lifted Klein‑family value #A8BEF0 for permission‑prompt text that actually needs to be read.

Lc: 91   (passes body gate)

Strictness of the Variations

• V3 Prot is the only variation where every accent passes the strict APCA gates.
• The other themes make deliberate trade‑offs:
  • Gallery sacrifices strict accent contrast for aesthetic reasons.
  • Refined and Sand & Sea sit in between, balancing contrast and visual style.

Usage Constraints

The themes work only when Claude Code’s /theme picker is set to dark‑ansi. On any other setting, Claude Code ignores the ANSI palette and renders its hard‑coded RGB values instead.

Installation

• Built for macOS Terminal.app.
• Ships as .terminal profile files with an Objective‑C builder, install.sh, and a restore.sh script that rolls back your previous profile.

Repository

https://github.com/robertnowell/klein-blue