High colour contrast refers to a significant difference in appearance between two colours placed next to each other. This difference makes text, images, or other visual elements stand out clearly against their background.
Understanding Colour Contrast
Colour contrast isn't just about aesthetics; it's a crucial factor in visual perception and accessibility. When the difference between colours is high, it's much easier for people to read text, distinguish elements, and understand visual information, especially for individuals with visual impairments or colour deficiencies.
How Colour Contrast is Measured
Contrast is typically expressed as a ratio. This ratio quantifies the difference in luminance (brightness) between two colours. A higher number in the ratio means a greater degree of contrast between the two colors.
- Ratio Scale: Contrast ratios range from 1:1 (no contrast, like white text on a white background) up to 21:1 (maximum contrast, like black text on a white background).
- High Contrast: A high contrast ratio is typically closer to the maximum of 21:1.
Examples of Colour Contrast Ratios
To illustrate the concept of contrast ratios, consider these examples from the reference:
| Colour Combination | Contrast Ratio | Level of Contrast |
|---|---|---|
| White and Black | 21:1 | Very High (Highest Possible) |
| White and Yellow | 1.07:1 | Very Low |
- As shown, white and black have a contrast ratio of 21:1 (the highest possible), indicating maximum distinction.
- In contrast, white and yellow have a contrast ratio of just 1.07:1, showing very little difference and making readability difficult.
Why High Contrast Matters
High colour contrast is essential for:
- Accessibility: It helps people with low vision, colour blindness, and age-related vision changes to perceive information clearly.
- Readability: Text with sufficient contrast is easier and faster to read for everyone.
- Usability: Clear contrast helps users understand which elements are interactive and how to navigate interfaces.
Using colour combinations with high contrast ratios ensures that visual content is perceivable and understandable to the widest possible audience.
