Color Accessibility

Greg KrausUniversity IT Accessibility Coordinator

North Carolina State Universitygdkraus@ncsu.edu

@gdkraus

Concepts

Two Questions We Ask With Color Accessibility

1. Given moderate visual acuity loss, can a person read this content without the aid of assistive technologies?

2. If a person needs an assistive technology, does our content prevent them from modifying the content to meet their needs?

Planning for Color and Visual Deficiencies

• There are a wide range of color deficiencies and visual impairments

• How do we plan for them all?

Visual Impairment Simulator

• NoCoffee• Chrome Extension

Standards: Taking the Guessing Out of Conformance

• WCAG 2– Color is not the sole means of conveying

information– Provide sufficient contrast based on the size of the

text and the conformance level desired

WCAG 2 (1.4.1): Use of Color

• Level A• Examples of violations– “Required fields are in red”– “Complete the blue section first”

WCAG 2 (1.4.3 and 1.4.6): Contrast

• Level AA and Level AAA Conformance• Ratios– 3:1 minimum acceptable contrast for standard text and

vision– 4.5:1 accounts for moderately low visual acuity (vision

loss equivalent to approximately 20/40)• typical visual acuity of people at roughly age 80

– 7:1 accounts for users who typically do not depend on assistive technologies for visual impairments (vision loss equivalent to approximately 20/80)

What Is Covered in WCAG Contrast Requirements?

• Text• Does NOT apply to– Logos– Inactive form elements– Purely decorative text– Incidental text in photos– Other UI elements

WCAG 2 Conformance Levels and Ratios

• Level AA– 18 pt. or 14 pt. bold 3:1– Smaller, 4.5:1

• Level AAA– 18 pt. or 14 pt. bold 4.5:1– Smaller, 7:1

• 18pt (1.5em, 150%)• 14pt (1.2em, 120%)

Beyond WCAG 2

• (Acknowledge Wayne Dick from CSU Long Beach for information)

• There is no average person with low vision• 35+ critical structures in the human visual

system– Multiple ways these structures can break

• Bright light is painful to many people with low vision

What Else To Consider

• Practice strict separation of presentation from content

• Anticipate users changing your color scheme• Potentially provide text enlargement with

reflow to 300% (WCAG 2 AA only requires 200%)

Tools

Eyedropper Tools

• Colour Contrast Analyser• Desktop application for Windows and OS X• Strengths– Can choose any colors on the screen

• Weaknesses– Anti-aliasing of text– Text over a non-uniform background– Must manually check elements

Colour Contrast Analyser

Automated Tools

• WAVE• Juicy Studio Accessibility Toolbar• Strengths– Automatically checks all color combinations– Can account for text size

• Weaknesses– Text over images– Text in images– Text over CSS3 gradients

Text Over Images

Anti-Aliased Text

Image Analysis

• Color Contrast Analyzer for Chrome• Chrome extension• Strengths– Checks the page as it is rendered

• Weaknesses– Cannot differentiate between text and other user

interface elements

Color Contrast Analyzer: Original Image

Color Contrast Analyzer: Mask

Color Contrast Analyzer: Text Over Images

Color Contrast Analyzer: Text in Images

Testing Color Palettes

• NC State Accessible Color Palette Evaluator• Web-based application• Build a color palette• Compare all of the color combinations to see

which have enough contrast• Sample Accessible Palette Evaluator

Color Palette Extractor

• Color Palette Extractor• Detects all of the colors defined in a page• Populates the Color Palette Evaluator

Color Palette Tweaker

• Tanaguru• Web-based application• Pick two colors and adjust one of them to

make the contrast great enough to meet WCAG

Substituting Style Sheets

• Web Evaluation Tools

Questions