Itten's 12-hue color circle places complementaries diametrically opposite and is constructed from pigmentary primaries, not spectral primaries

Itten constructs a 12-hue circle from three pigmentary primaries (yellow, red, blue) placed in an equilateral triangle, with secondaries (orange, green, violet) in alternating positions and six tertiaries filling the remaining slots. The key design choice: complementary colors are diametrically opposite — their pigment mixture gives gray. This differs from Ostwald’s circle (where blue sits opposite yellow, giving green on mixing — useless for painting). The 12 hues should be internalized as precisely as a musician knows the chromatic scale’s 12 tones. The circle is the reference for all contrast types: hue distances define contrast strength; diameter defines complementary pairs; equilateral triangle inscriptions define harmonic triads; squares and rectangles define harmonic tetrads. Delacroix kept one on his studio wall labeled with possible combinations.

Examples

In GLSL: parameterize hue as an angle 0-360 on the circle; complementary = hue + 180; triadic = hue, hue+120, hue+240; split-complementary = hue+150, hue+210. Use HSL/HSV color space for circle navigation.

Assessment

Construct the 12 hues in order from yellow; explain why Ostwald’s circle is ‘not serviceable to painting’; identify the equilateral triangle formed by the three primaries and the one formed by the three secondaries.