Each hue has a perceived brightness (luminosity) that peaks at yellow/cyan/magenta and dips at red/green/blue

Even at identical HSB brightness and saturation, different hues appear different brightnesses to the human eye. This is called luminosity. Yellow, cyan, and magenta are the highest-luminosity hues; red, green, and blue are the lowest-luminosity hues. The practical implication for color variation: when making a darker variation of a color, shift hue toward its nearest luminosity minimum (red, green, or blue) — this reinforces the perceptual darkening from lowering HSB brightness. For a lighter variation, shift toward the nearest luminosity maximum (yellow, cyan, or magenta). This makes the hue shift work with the brightness/saturation shift rather than fighting it. Hue is secondary, though — you can often ignore it and still get good variations from brightness and saturation alone.

Examples

A coral at 21° hue sits between red (0°, luminosity minimum) and yellow (60°, maximum). For a shadow (darker variation), hue shifts down toward red at 0°. A teal at 194° sits between green (120°) and blue (240°); shadow hue shifts up toward blue at 240°.

Assessment

Given a lime green at H=90°, identify its nearest luminosity minimum and maximum, and describe the hue shift direction for both a darker and a lighter variation. Explain why this hue shift matters even when brightness/saturation are already adjusted correctly.