When selecting colours for a webpage, the visual difference between content colour (text, graphs, images, etc.) and background colour (i.e., the minimum luminance contrast ratio) must adhere to the following standards:
4.5:1 for regular-sized text (10 pt – 12 pt font)
3:1 for large-sized text (14 pt font and larger)
When highlighting important items on a webpage, two or more characteristics should be used to differentiate them from other items on the page (e.g., making a required field bold and red), as colour alone must not be used to visually distinguish elements.
Additionally, it is essential to indicate both the font colour and background colour used on a page to help users with visual disabilities who adjust browser settings to modify webpage colours.
CEL Accessibility Guidance (derived from WCAG 2.0) Addressing the Use of Colour: