Color in digital systems is fundamentally about how displays produce the sensation of color in the human visual system. Modern screens use additive color mixing, combining red, green, and blue light at varying intensities to stimulate the three types of cone cells in the retina. The RGB model directly maps to this hardware reality, with each channel represented as a value from 0 to 255 (8 bits per channel), yielding approximately 16.7 million possible colors in the standard 24-bit color depth. HEX notation is simply a hexadecimal representation of these same RGB values, with #FF5733 translating to R=255, G=87, B=51.

While RGB and HEX are hardware-centric, the HSL (Hue, Saturation, Lightness) and HSV/HSB (Hue, Saturation, Value/Brightness) models are designed around human color perception. Hue represents the fundamental color as a position on the color wheel (0-360 degrees, where 0 is red, 120 is green, and 240 is blue). Saturation describes color intensity, from gray (0%) to full vibrancy (100%). The key difference between HSL and HSV lies in the third component: HSL's Lightness ranges from black (0%) through the pure hue (50%) to white (100%), while HSV's Value ranges from black (0%) to the full-intensity hue (100%). HSL is generally more intuitive for CSS development because adjusting lightness produces predictable results, while HSV is preferred in design applications like Photoshop because its brightness control better matches artistic expectations.

The CMYK model (Cyan, Magenta, Yellow, Key/Black) operates on subtractive color mixing principles used in printing. Unlike screens that emit light, printed materials reflect light, and each ink absorbs certain wavelengths. CMYK values cannot be directly converted to RGB without a color profile because the relationship depends on specific ink and paper characteristics. This fundamental difference between additive and subtractive color systems means that not all screen colors can be accurately reproduced in print and vice versa, a limitation known as the gamut boundary.

Color spaces define the range (gamut) of colors that can be represented and the mathematical relationship between color values and actual perceived colors. sRGB, the standard for web content, represents a relatively narrow gamut. Display P3, used by modern Apple devices, covers approximately 25% more colors. The CIE Lab and oklch color spaces are perceptually uniform, meaning that equal numerical changes produce equal perceived color differences regardless of where you are in the color space. This perceptual uniformity makes them superior for generating harmonious color palettes, creating smooth gradients, and calculating accessible contrast ratios.