A generic similarity score called an off-brand red 97% on-brand. Real color science measured it 7.12 off and blocked it. That gap is the whole point of the Brand Fidelity Firewall. Brands now ship hundreds of AI-assisted campaign variants a week, and every one is a chance to send out the wrong red, a cramped logo, or an ad with no required AI-disclosure label. A "looks-fine" aesthetic score can't tell a correct Pantone from a competitor's. Color science can. So we built a pre-ship gate, not a rubber stamp. Every asset is measured in real CIEDE2000 (ΔE00), the ISO/CIE-standard color-difference metric, against the brand's exact per-color Pantone tolerance. In the demo, one holiday asset's hero red came in at ΔE00 7.12 off Lumiere Crimson (PMS 484), well past the 3.0 tolerance. Hard BLOCK. The generic perceptual-hash baseline sitting right beside it rated that same asset 0.97 on-brand. It would have shipped. The gate returns PASS, FLAG, or BLOCK, each backed by an objective measurement, and the decision is deterministic code outside the model. The LLM only advises; the gate decides. Every cleared asset exports a Brand Fidelity Certificate you can file. On the fixed 12-asset demo batch, 7 assets auto-cleared, 3 were blocked, and 2 were flagged for a human to own. Lumiere is a synthetic brand and the assets are synthetic, built so every check measures real pixels. 🎨 If your team is thinking about how to govern on-brand, compliant creative at AI volume, we'd genuinely like to hear how you're approaching it. The problem is industry-wide, and so are the answers. #BrandGovernance #CreativeOps #AICompliance #ColorScience #MarketingOps