What color criteria is specified for items that need to be identified solely by color?

Identifying items solely by color requires ensuring that there is sufficient contrast between the items. This is crucial for accessibility, as individuals with visual impairments or color blindness may not distinguish colors effectively. By maintaining a significant contrast, it allows all users to easily perceive the items in question, reducing the risk of confusion or misinterpretation.

While having complementary colors can be visually appealing and can help with contrast, the essential requirement is that the contrast must be sufficient for accessibility purposes. Moreover, stating that colors must be primary or can be any shade does not address the accessibility concerns, as these options do not guarantee that individuals with visual impairments will be able to differentiate the items. Hence, ensuring sufficient contrast is the fundamental criterion for items identified by color to accommodate a wider range of visual abilities.