1.4.1 Use of color
Make it easier for users to see and hear content including separating foreground from background.

About

Color is an important element of design and should naturally be used. If the information is presented using only color, a person who cannot distinguish color will not have access to the information. For example, use color-coded asterisks to indicate required values on a form page, not color-coded field labels.

Example:

Before Rectification

image with color-coded field labels.

After Rectification

image with color-coded asterisks to indicate required values.