
ARBE λ* (Absorption–Reflection Balance Edge) is the wavelength where a color absorbs and reflects light equally—a physical fingerprint of color, more reliable than visual appearance. Found via the Brent method, λ* enables practical uses: ensuring accessibility, detecting metamerism, verifying safety colors, and revealing forgery. It’s a foundation for making color trustworthy across industries.
📇 ARBE λ* Atlas – GPT Cards

🟦 Card 1 – ARBE λ*: Brent Calculator
Discover the balance point of light. This GPT calculates ARBE λ* – the exact wavelength where absorbed and reflected energy are equal – using the robust Brent method.
What you can do:
Try with a flat spectrum (λ* ≈ 555 nm)
Upload your own spectrum data
Learn why λ* is a fingerprint of color

🟩 Card 2 – ARBE λ*: Metamerism Checker
Two colors may look the same – but are they really?
This GPT checks whether two colors share the same spectral identity – or are metameric.
What you can do:
Compare two spectral reflectance curves
Detect if colors are metameric (visually identical, physically different)
Understand why λ* reveals what CIELAB sometimes hides

🟩 Card 3 – ARBE λ*: Safety Color QC
Check the reliability of warning colors. This GPT verifies if a spectrum lies inside the λ* safety window for critical safety tones.
What you can do:
Validate firetruck red (λ* ≈ 590 – 610 nm)
Test safety yellow (λ* ≈ 570 – 585 nm)
Learn why λ* makes safety measurable

🟨 Card 4 – ARBE λ*: Spectral Cluster Tool
Find harmonious color groups with a shared spectral identity.
This GPT clusters colors from the ARBE λ* Atlas according to their spectral balance wavelength and creates harmonized palettes.
What you can do:
🎯 Cluster HLC colors with similar ARBE λ* (± Δλ)
🎨 Create palettes with spectral coherence
🧠 Understand how λ* proximity supports harmonious feeling
🗂️ Export the clusters as JSON, CSS tokens or PNG swatches

🟨 Card 5 – ARBE λ*: Accessibility Contrast
Keep interfaces readable across lighting. This GPT builds AA/AAA text–background pairs from the ARBE* Atlas and controls λ* separation so colors remain stable beyond a single display profile.
What you can do:
♿ Build AA/AAA pairs with WCAG targets
↔️ Set λ* proximity thresholds (e.g., ≥ 25 nm)
🧭 Snap any HEX/Lab to official Atlas samples (Hybrid: Sample · HEX · Lab · λ*_V2)
📦 Export as JSON tokens, CSS variables, or PNG swatches