A Provisional Conceptual Framework for Mucosal Colour Assessment in Terrestrial Mammals.

Mucosal colour assessment is widely used in veterinary medicine as an indicator of physiological states, but current approaches are characterized by inconsistent terminology, variable methodology, and differing levels of validation. This communication introduces the provisional Uldahl Standard, a conceptual framework developed to improve consistency, transparency, and reproducibility in mucosal colour assessment in terrestrial mammals. The framework integrates principles from veterinary medicine, colorimetry, and modern imaging technologies, combining perceptual, computational, and instrument-based approaches to colour analysis. Mucosal colour assessment is defined as a multidimensional process comprising colour category, light saturation level, physiological association, assessment method, and level of validation. Nine principal colour categories and eight standardised saturation modifiers were identified through a literature review and incorporated into the framework. The standard further emphasizes transparent reporting of assessment conditions, validation procedures, artefact evaluation, and analytical pathways, including examples using AI-assisted visual analysis. The framework acknowledges the inherent variability in mucosal colour assessment arising from environmental conditions, limitations of human colour perception, and differences in descriptive methods while providing a structured and comparable terminology, linked to defined levels of validation. It is anticipated that application of the proposed Uldahl Standard will provide markedly more robust and consistent descriptions of mucosal colours, which, provided they are combined with well validated clinical signs of the underlying physiology and/or pathophysiology, will greatly enhance the diagnostic power of the procedure.