Protanopia (Red-Blind)

People with protanopia have no red photoreceptors (L-cones). Red appears dark and can be confused with black or dark gray. Red and green are difficult to distinguish. Affects about 1% of men.

Deuteranopia (Green-Blind)

People with deuteranopia have no green photoreceptors (M-cones). This is the most common type of color blindness. Red, orange, yellow, and green all appear similar. Affects about 1% of men.

Tritanopia (Blue-Blind)

People with tritanopia have no blue photoreceptors (S-cones). Blue and green appear similar, as do yellow and violet. This is very rare, affecting about 0.01% of people equally across genders.

1. Don't Rely on Color Alone

Use text labels, icons, patterns, or shapes in addition to color. For example, use checkmarks for success instead of just green.

2. Ensure Sufficient Contrast

Maintain WCAG-compliant contrast ratios (4.5:1 for text). High contrast helps everyone, including color-blind users.

3. Test Red-Green Combinations

Red-green is the most problematic combination. Avoid using red and green as the only differentiators (e.g., for success/error states).

4. Use Color-Blind Friendly Palettes

Choose colors that remain distinguishable. Blue and orange work well together. Avoid pure red and green.

5. Add Patterns and Textures

In charts and graphs, use different patterns (stripes, dots) in addition to colors for data series.

6. Provide Alternative Indicators

Use underlines for links, icons for status, and explicit labels for form validation.

Instead of: Red border for errors, green for success

Use: Red border + error icon + "Error:" text prefix for errors
Green border + checkmark icon + "Success:" text prefix for success

Instead of: Only using different colors for pie chart segments

Use: Colors + patterns + clear labels with percentages

Instead of: Only changing link color

Use: Color + underline + different font weight