Why HSV beats RGB for photo color replacement in browser-based image tools

A developer building browser-based image editing tools explains why the common RGB Euclidean distance method fails for color replacement on real photographs. The core problem is that shadows and highlights of the same color have vastly different RGB values, forcing an unworkable tradeoff between over-selecting and under-selecting pixels. Switching to the HSV color model solves this by isolating hue from brightness, allowing tight color matching regardless of lighting variation. The developer also recommends preserving the original pixel's saturation and value when filling replaced pixels, so shadows, highlights, and fabric texture remain intact. Separate tolerance sliders for hue, saturation, and value are advised over a single threshold control for more precise and practical tuning.