Yes, Siteimprove checks for color contrast issues in Accessibility using guidelines described below.
The color contrast ratio required depends on the level of conformance you wish to reach. Level AAA conformance is more strict that AA.
- AA Guideline 1.4.3 Contrast (Minimum): The contrast ratio should be at least 4.5:1 for normal text and 3:1 for large text.
- AAA Guideline 1.4.6 Contrast (Enhanced): The contrast ratio should be at least 7:1 for normal text and 4.5:1 for large text.
Insufficient contrast between text and its background can create difficulty for visually impaired or color-blind users. In general, sufficient contrast is good practice as insufficient contrast can affect all users leading to important text being overlooked.
Note: Contrast measurements are not relevant where content is hidden. However, the contrast ratio should be sufficient for hidden content which becomes visible when receiving focus.