Blue-grey vs blue eyes

A clear blue iris reads as a definite colour; blue-grey reads as a blue that has had the saturation taken out of it. Placed side by side the difference is usually obvious; seen separately, the same eyes are often called blue by one person and blue-grey by another.

Typical distribution

Both are generally even. Blue often shows more contrast between a lighter inner zone and a darker limbal ring than blue-grey does.

Undertone

Blue is cool and comparatively saturated; blue-grey is cool and markedly desaturated, sitting between blue and neutral.

Central or outer ring

A pronounced limbal ring is more commonly noted on clear blue irises, but it occurs in both and is not a reliable separator.

Lighting effects

Blue-grey shifts more, because it has less colour of its own to resist the influence of surroundings. A blue shirt can make blue-grey eyes read as convincingly blue.