NLLB traces a cross-lingual color circle plus luminance axis

Mathewson probes NLLB-200 (distilled 600M), a 200-language encoder-decoder translation Transformer, extending coverage beyond decoder-only LLMs [mathewson-2026-nllb-multilingual-geometry] Embedding the 11 Berlin & Kay basic color terms across 136 languages, PCA's first two components recover a circular hue arrangement with a warm/cool opposition matching color-wheel structure [mathewson-2026-nllb-multilingual-geometry] A third principal component forms an axis orthogonal to the hue plane separating achromatic terms (white/black/grey) from the chromatic ring [mathewson-2026-nllb-multilingual-geometry] The shape (hue circle plus orthogonal lightness axis) matches the Llama-3.1-8B color paraboloid qualitatively, but here the two dimensions are orthogonally separate rather than fused into a paraboloid [mathewson-2026-nllb-multilingual-geometry] The finding is purely representational (PCA projection only), with no causal steering, across 136 typologically diverse languages [mathewson-2026-nllb-multilingual-geometry]