Don't use color to convey content- Color provides great design advantages, but when it is relied on to convey content — it can be ineffective. Non-visual and visual users who cannot access color must be taken into account when using color to emphasize elements. Information conveyed with color must also be communicated textually to be effective.
The use of color alone to convey information - Using color alone to convey information is not recommended because it creates accessibility issues for people with low vision, color blindness, or those who cannot perceive color.
Contrast - Make sure foreground and background colors and other visual indicators contrast each other. Understanding just a little bit about color and contrast can help you communicate more effectively in your documents, web pages, and presentations.