Does a red call-to-action button increase conversions?

Yes. Red CTAs consistently outperform other colors in A/B tests, with conversion rate improvements of 10-30% over green and blue alternatives. This is attributed to red's attention-grabbing properties and urgency associations. However, results depend on surrounding context and cultural audience.

What is red's complementary color?

In the RGB (additive) color model, red's complementary color is cyan. In the traditional RYB (subtractive) model used in painting, red's complement is green. Both pairings create maximum contrast and visual tension when placed together.

How do I make red text accessible (WCAG compliant)?

Red text requires a minimum contrast ratio of 4.5:1 against its background to meet WCAG AA standards. Dark reds like #8B0000 (dark red) or #660000 pass against white. Bright red #FF0000 on white achieves only 3.99:1 and fails AA. Use WebAIM's Contrast Checker to verify specific combinations.

What percentage of people are red-green colorblind?

Approximately 8% of men and 0.5% of women have red-green color blindness (deuteranopia or protanopia). This means roughly 1 in 12 male users cannot reliably distinguish red from green. Always pair color-coded information with icons, labels, or patterns as a secondary encoding.

Color Theory: Working with Red

Red on the Color Wheel

Red sits as a primary color in both traditional (RYB) and modern (RGB/additive) color models. In the HSL color space, pure red is defined as hue 0° (or 360°), with full saturation producing the most vivid expression. Red's complementary color is cyan (in RGB) or green (in RYB), creating maximum contrast and visual tension when paired. This complementary relationship is why red-green combinations are so eye-catching — and why they present the most common accessibility challenge for color-blind users.

Palettes and Combinations

Analogous: Red paired with red-orange and red-violet creates warm, harmonious palettes ideal for conveying energy and passion. Triadic: Red with blue and yellow produces vibrant, balanced compositions — the foundation of countless brand identities and superhero costumes. Split-complementary: Red with blue-green and yellow-green offers contrast without the starkness of a full complementary scheme, making it easier on the eyes while retaining visual impact.

Practical Guidelines

Call-to-action buttons: Red CTAs consistently outperform other colors in A/B tests, with conversion rate improvements of 10-30% over green and blue alternatives
Text legibility: Red text on white backgrounds requires a minimum contrast ratio of 4.5:1 (WCAG AA). Dark reds (#8B0000, #660000) pass; bright reds (#FF0000) often fail
Cultural awareness: Verify red's meaning in your target audience — financial gain in China (red = up), financial loss in the West (red = down)
Proportion: The 60-30-10 rule works well with red as the 10% accent. Overusing red fatigues the eye and dilutes its attention-grabbing power
Accessibility: Approximately 8% of men and 0.5% of women have red-green color blindness (deuteranopia/protanopia). Never rely on red alone to convey meaning — pair with icons, labels, or patterns

Color Theory: Working with Red

Red on the Color Wheel

Palettes and Combinations

Practical Guidelines

Frequently Asked Questions