SpeedDrain
Brettel / Viénot Matrix · WCAG 2.2 Compliant

Color Blindness Simulator

Verify accessibility for the 300+ million people with color vision deficiencies. Test custom UI palettes, compute WCAG contrast ratios, and inspect screenshots locally.

Simulation Comparison

Normal Vision

92% of world
Trichromatic

Standard human trichromatic color vision with full RGB sensitivity.

Primary TagAccent Tag

Sample UI typography rendering under Normal Vision.

#dc2626
Contrast:4.83:1Pass AA

Protanopia (Red-Blind)

~1% of males
Dichromatic (L-Cone)

Absence of red L-cones. Reds appear dark, brownish, or olive green.

Primary TagAccent Tag

Sample UI typography rendering under Protanopia (Red-Blind).

#8d8c26
Contrast:3.55:1Fail

Deuteranopia (Green-Blind)

~1.2% males (Deutans ~6%)
Dichromatic (M-Cone)

Absence of green M-cones. Most prevalent form of red-green deficiency.

Primary TagAccent Tag

Sample UI typography rendering under Deuteranopia (Green-Blind).

#98a526
Contrast:2.71:1Fail

Tritanopia (Blue-Blind)

<0.01% of population
Dichromatic (S-Cone)

Absence of blue S-cones. Blues appear greenish, yellows appear light gray or violet.

Primary TagAccent Tag

Sample UI typography rendering under Tritanopia (Blue-Blind).

#d32626
Contrast:5.15:1Pass AA

Achromatopsia (Monochrome)

1 in 33,000
Monochromacy

Complete lack of cone function. Vision is entirely shades of black, white, and gray.

Primary TagAccent Tag

Sample UI typography rendering under Achromatopsia (Monochrome).

#5c5c5c
Contrast:6.69:1Pass AA

Designing for Color Vision Deficiency (CVD)

The 4 Major Color Vision Deficiencies

Human color perception depends on three retinal photoreceptor cone types: L-cones (long/red), M-cones (medium/green), and S-cones (short/blue). Deficiency in one or more cone types creates specific forms of color blindness:

  • Deuteranopia: Caused by absent green M-cones, affecting approximately 1 in 12 men. Red, orange, and green shades appear yellowish-brown.
  • Protanopia: Caused by absent red L-cones, affecting roughly 1% of men. Pure reds appear dark or black, and distinctions between red and green are lost.
  • Tritanopia: An uncommon autosomal condition causing loss of blue S-cones. Blues appear greenish and yellows appear pink or violet.
  • Achromatopsia: Total cone monochromacy where individuals perceive exclusively brightness and contrast shades.

WCAG Success Criterion 1.4.1: Use of Color

WCAG Guideline 1.4.1 dictates that color must never be the sole visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.

Actionable Best Practices:

  • Pair error notifications with exclamation icons (⚠️) or text labels, not red backgrounds alone.
  • In data charts, combine unique color fills with dashed vs. solid strokes or distinct point markers.
  • Ensure text meets WCAG AA contrast of at least 4.5:1 against its background even when simulated in grayscale.