Your color as a brand: the primary, the secondary colors from the chosen scheme, lighter and darker versions for backgrounds and states, and the neutrals from night to paper through greys tinted with your hue. Copy it as CSS.
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
AaInk on ≈ PeriwinkleLc 57 · large textWCAG 2 · 8.3 : 1 · AAA
Aa≈ Periwinkle on InkLc 55 · large textWCAG 2 · 8.3 : 1 · AAA
Avoid
AaClub Soda on ≈ PeriwinkleLc 41 · display sizesWCAG 2 · 2.1 : 1 · fails
Aa≈ Periwinkle on Club SodaLc 37 · display sizesWCAG 2 · 2.1 : 1 · fails