Read more about levels of conformance at WCAG.

For a given WCAG level, calculate whether two colors have enough contrast with each other to be used together (e.g., as a background and text color combination).

To meet AA level sufficiently, follow these standards. To meet AAA level sufficiently, follow these standards.

TODO (consider this a headsup on likely API changes!):

• Use named fontweights rather than numbers
• Wrap fontsize with some constructors
• Cassowary constraint solving..?

Calculate the contrast between two colors.