Redundant coding must also be used with symbols. Shape-coding combined with color-coding is often an effective means of redundantly coding symbols. When small symbols are used on a display, even persons with normal color vision may have difficulty distinguishing some colors, such as differentiating "yellow" from "white" or in discerning "blue." At times, it is appropriate to use text to label symbols and/or icons. Alpha-numeric characters are a special form of symbol.

	Heavy Airplane
	Medium Airplane
	Helicopter
	Balloon
Redundant Coding by Color and Shape