To find insufficient color contrast, look for text in your document that’s hard to read or to distinguish from the background.
If unsure, use the Colour Contrast Analyzer, a free app that analyzes colors and contrast, and displays results almost immediately.
To check that you have chosen the correct color contrast ratio, grag the Foreground eyedropper icon over a sample of your text or image of text. Drag the Background eyedropper icon over a sample of your background color. If the contrast ratio does not pass, then adjust your foreground or background until it does pass.