The color of the text and the color of the background are not in sufficient contrast to each other.
The contrast ratio should be at least 4.5:1 for normal text and 3:1 for large text.
Note: Contrasts are not relevant where content is hidden. But make sure that for hidden content which becomes visible when receiving focus, the contrast ratio is sufficient.
Insufficient contrast between text and its background can give problems for users with visual impairments and color blindness, but it can also affect a lot of other users, leading users to potentially overlook important text.
It's important to ensure foreground and background colors have enough contrast so that people with low vision, color blindness, or other visual impairments can read your content. When contrast is insufficient, it becomes difficult for many people with and without visual impairments to clearly read or understand your content. For example, the "Getting Started" text below has insufficient contrast and thus is difficult to read.

To meet WCAG AA compliance for color contrast, visual presentation of text and images of text must have a contrast ratio of at least 4.5:1 (with some exceptions). There are handy tools available online, such as Accessible Colors and the WebAIM Color Contrast Checker to confirm whether your color combinations meet accessibility guidelines.
If you're unsure what color your text or background is, right-click it and select "Inspect". In the "Styles" section of the dialog box, there should be an option titled "color" or "background-color". See below for an example. This will tell you the exact colors for contrast testing.
