[raymondk]

The payment QR code was drawn in the terminal's own colours, so a light theme inverted it and a dark theme often gave grey on near-black; many phone cameras read neither.

When stderr has colour support, every row of the drawing is now set to 256-colour palette entry 231 (white) on entry 16 (black), which sit in the fixed colour cube that themes do not remap, and reset at its end. The qrcode crate still does the encoding and the half-block layout; this only wraps its rows. The terminal-size fit check still measures the plain drawing. Without colour support the plain drawing is printed as before, so the worst case is today's output.

This is the small alternative to #824's hand-rolled coloured renderer. Unit test the_qr_code_is_coloured_black_on_white_row_by_row.

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Part of restacking #824 into small PRs, one fix each, stacked on main in this order: cycles-buy/01-json-implies-yes → 02-arg-group → 03-gateway → 04-qr-colours → 05-paste-flags → then the wait, its follow-up text and the --json fields. Each PR targets the one below it; after the one below merges, retarget to main.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Twxau844tMTwyHpQJEbmBo

[Copilot]

🟢 Approval recommended

The focused change preserves existing layout and fallback behavior, with no unresolved findings.

No open issues 🎉

What changed in this PR

Makes the icp cycles buy payment QR code readable across terminal themes without replacing the existing renderer.

Changes:

• Applies fixed black and white colours to each row, resetting afterward.
• Preserves plain-output fallback and terminal-size checks.
• Adds a regression test and changelog entry.

File	Description
crates/​icp-cli/​src/​commands/​cycles/​buy.rs	Adds conditional QR colouring and a row-by-row regression test.
CHANGELOG.md	Documents the QR readability fix.

_{Review effort: Balanced}