Why IKB Fails as Terminal Text (and How I Split It Across Two ANSI Slots)

Most terminal themes are built for code. Mine is built for Claude Code, which means most of what I read in it is prose — tool output, reasoning traces, permission prompts. After a few months of daily sessions, the default theme started feeling wrong in a way I couldn't immediately name.

The problem I eventually landed on: no one had tuned an ANSI theme for the specific slots Claude Code actually uses. So I built klein-blue — four Terminal.app variations anchored to Yves Klein's International Klein Blue pigment.

The interesting constraint is that pure IKB fails as text on a dark ground. APCA Lc -12. That's not a borderline fail — it's effectively absent. Which creates a real design problem when the whole point is IKB.

The fix I settled on: split the pigment across two ANSI slots with different jobs.

ansi:blue 002FA7 — decorative only: borders, dividers, highlights