The ContrastChecker script helps to select color pairs for text and backgrounds, icons and other interface elements, diagrams, and to check the contrast of color pairs for compliance with WCAG 2.1 (Web Content Accessibility Guidelines) criteria.
The Hue-Saturation-Brightness (HSB) sliders are available in the script dialog for manual color correction. The Custom button automatically tries to correct the saturation and brightness of both colors to the specified contrast value.
Color contrast is an important parameter that is difficult to define precisely. You can use the ContrastChecker script to check contrast in Illustrator according to the WCAG standard. If you're not sure, use other algorithms, such as APCA, and your own experience to support your results.
Keep in mind that contrast can vary based on monitor, device, environmental conditions, font design, and a host of other details. Using common sense may be more helpful than mindlessly following a rule of thumb.