Approximating contrast-color() With Other CSS Features

The CSS Color Module Level 5 draft introduces the contrast-color() function, but with limited browser support, CSS-Tricks has found an alternative implementation using other new CSS features, such as color spaces and the oklch() function. The contrast-color() function aims to calculate the optimal text color based on the background color, ensuring sufficient contrast for readability.

Why This Matters

The Web Content Accessibility Guidelines (WCAG) provide formulas for calculating contrast between colors, but these formulas are complex and not easily translatable to CSS. The contrast-color() function simplifies this process, but its limited support necessitates alternative solutions. By using other CSS features, developers can achieve similar results, ensuring their websites are accessible and readable for all users.

Key Insights

The oklch() function can be used to approximate the contrast-color() function, with a threshold of 0.65-0.72 for OKLCH lightness.
The color-mix() function can be used to mix two colors, allowing for more flexible contrast calculations.
CSS Custom Functions can be used to simplify the implementation, but their limited support requires careful consideration.

Working Example

color: oklch(from <your color> round(1.21 - L) 0 0);

This example uses the oklch() function to calculate the optimal text color based on the background color, with a threshold of 0.65-0.72 for OKLCH lightness.

Practical Applications

Use Case: A website with a configurable background color can use this technique to ensure sufficient contrast between the background and text colors.
Pitfall: Failing to consider the limitations of CSS features and browser support can result in inconsistent or inaccessible implementations.

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Approximating contrast-color() With Other CSS Features