ContrastGraded by APCA, the Accessible Perceptual Contrast Algorithm, which measures how strongly text stands off its ground the way eyes see it, as lightness contrast (Lc) from 0 to about 106. Lc 60 and up reads as body text, 45 to 60 as large text and headlines, 30 to 45 at display sizes only (a logo, a big headline); under 30, avoid it for text. The same measure picks black or white text everywhere on Chromary. The older WCAG 2 ratio and its grade (AAA, AA, AA large) are shown small under each for anyone working to that standard.
Use
AaChalk on ≈ CementLc 59 · large textWCAG 2 · 3.0 : 1 · AA large
Aa≈ Cement on ChalkLc 54 · large textWCAG 2 · 3.0 : 1 · AA large
Avoid
AaCharcoal on ≈ CementLc 42 · display sizesWCAG 2 · 5.6 : 1 · AA
Aa≈ Cement on CharcoalLc 40 · display sizesWCAG 2 · 5.6 : 1 · AA
HarmoniesWays to pair this color with others by where they sit on the color wheel: its opposite, shapes of two to four colors spaced around the wheel, its neighbors on either side, then the same hue lighter, darker, warmer, cooler and quieter. Each strip leads with this color. Tap one to open its kit built that way.