Color is sometimes used to convey meaning beyond the basic text. In a course syllabus, for example, you may use color to emphasize an important statement. Or, on a PowerPoint slide showing a multiple choice question, you might show the correct answer in green and color the incorrect answers in red. Using color to communicate meaning or emphasis is problematic for students with color blindness. If you want to use color to express meaning, you should also provide a supplemental means to convey the information without color.
A related issue is contrast. People who have some vision loss may have difficulty discerning changes in contrast color. When choosing font and background colors, make sure the contrast is strong enough to enable those with some vision loss to read the text. If the background is dark, text should be a light color; if the background is light, text should be dark. Avoid neon colors altogether and test readability with multiple devices.
In a good example, survey results reported by gender would display data from males in a red font followed with an asterisk. Colorblind students could identify male data by the asterisks rather than the colored font.
A poor example might consist of a form in which required fields are denoted in red without any additional indicator that conveys the meaning.