This success criteria aims to ensure visitors with low vision can perceive text content on a color or image background with an acceptable level of contrast.
For bolded text 14pt and lower, or unbolded text 18pt and lower, conformance to this guideline calls for a minimum contrast ratio of 4.5:1 for text and images with text.
For bolded text greater than 14pt, or unbolded text greater than 18pt, conformance to this guideline calls for a minimum contrast ratio of 3:1 for text and images with text.
Not sure how to do the math and determine your text elements' contract ratios? Check out Colorable, a simple tool to calculate contrast ratio.
A. Contrast Ratio = 3.52
B. Contrast Ratio = 9.22
There are some exceptions to this guideline, including logo type, text that appears in an image and is not the primary purpose of that image, and text used purely for decoration.
When designing your site, try to be mindful of elements that rely exclusively on color to attract users' attention.