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The contrast ratio must be at least 4:5 against the background and 3:1 against adjacent colors.
Please see more detailed information on how to comply with this guideline.
Color Should Not Be Used as The Only Way to Convey Information
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Users with partial sight often experience limited color vision.
Some older users may not be able to see color well.
Users who have color-blindness benefit when information conveyed by color is available in other visual ways.
People using limited color monochrome displays may be unable to access color-dependent information.
Users who have problems distinguishing between colors can look or listen for text cues.
Please see more detailed information on how to comply with this guideline.
WCAG Related References
1.3.3 Sensory Characteristics (Level A)