The common mistake is treating neutrals as the absence of colour — a default, a placeholder, a safe choice. In reality, a neutral is a highly specific decision. Cool greys (blue-leaning) feel clinical and modern. Warm greys (yellow- or red-leaning) feel organic and approachable. A neutral chosen carelessly produces an interface that feels vaguely wrong without anyone being able to say why; a neutral chosen precisely is what makes the entire palette cohere.
In design systems, neutrals carry most of the surface hierarchy. They are the backbone of every dark mode — a carefully calibrated stack of surfaces, each step slightly lighter than the one beneath it, creating depth through luminance alone. The quality of a design system's neutrals is often what separates a polished product from a merely functional one. It is easy to pick a good primary colour; it is hard to build a neutral scale that works at every level of the stack.
The move toward warm neutrals in recent design trends — seen across products from Linear to Figma — reflects a broader reaction against the sterile blue-grey palettes that dominated digital design through the 2010s. Warm neutrals have personality without demanding attention. They make extended use more comfortable, and they tend to pair more naturally with the warm tones of photography and illustration. The choice between warm and cool is one of the most consequential, and most often under-deliberated, decisions in a brand's visual system.