Developments in image-based colorimetric analysis methods and applications of CIElab color space in pharmaceutical sciences: A narrative review

The evaluation of color in pharmaceutical materials and products serves as an essential method for assessing physical appearance, stability, and overall quality control. Any recognizable color change in pharmaceuticals may lead to failure in meeting quality objectives. Traditional visual examinations, while commonly used, are subjective and prone to inconsistency, making them inadequate for precise assessment. As a result, advanced instrumental techniques have gained prominence, with CIE (Commission Internationale de l'Eclairage) Lab color space being widely recognized for its accuracy and applicability. Developed by the International Commission on Illumination, the CIELab system characterizes color using three components: L (lightness), a⁎ (red-green axis), and b⁎ (yellow-blue axis), providing a quantitative, standardized approach for color measurement. This method has been extensively utilized in pharmaceutical research and industry for diverse applications, such as quality control, stability studies, and batch-to-batch consistency evaluations. The present review aims to discuss studies that have employed this method in pharmaceutical color assessment, and related quality control issues.