The WCAG formula/algorithm for determining the contrast between two colors uses the luminance of these colors. That is: sRGB is converted into linear RGB, then the different channels are multiplied with three weights (R 0.2126, G 0.7152, B 0.0722) and then added up to get the luminance.
return the number and 2 swatches, one c1 > c2 and the other c2 > c1, that say Tsubaki
return the number and 2 swatches, one c1 > c2 and the other c2 > c1, that say
Tsubaki