Georgia Tech Research Institute
Accessibility Assistant

Accessibility Assistant


Indicator Lights (2 of 4)

Issue: Color coding is sometimes used as the sole means of conveying information.

Two states of a status light on a kiosk are shown.  A single light conveys open or closed status by illuminating green when the machine is open, and red when the machine is closed.

Indicator lights that use only a change of color (especially when the change is between red and green or between blue and yellow) as the only method of conveying information may be difficult for color blind users and some users with low vision to discern. For example, if a two-state light is used, with green representing the ready state and red representing a fault state, a user with red/green colorblindness may not be able to determine if the device is ready or is in a fault state.

Populations Impacted: Users who are color blind; users with low vision.

Potential Solutions:
  • Do not use color pairs that are easily confused by color blind users to convey information. Red/green color blindness is most common; however, blue/yellow color blindness occurs occasionally. Total color blindness, where users are not able to perceive color and only see shades of grey, is extremely rare. Using color combinations other than red/green and blue/yellow to represent information will help avoid confusion among most users who are color blind.

  • Two states of a status light on a kiosk are shown.  Two separate lights convey open or closed status.  A green light is located beside a red light.  The green light illuminates when the machine is open, and the red light illuminates when the machine is closed.  'Open' and 'Closed' text labels appear on the lights.
  • Always provide a redundant alternative to color, such as text and/or location, that conveys the same information that the color conveys. Anywhere color coding is used, the message conveyed by that color coding should be conveyed through text as well, in order to ensure that color blind users have access to the same information that other users do. For instance, in the example used above, a text indication that says "Ready" when the copier is in the ready state could be provided. The text message would communicate the same information to a color blind user that the green light communicates to a non-color blind user.

Additional Comments: Although the solutions presented above will improve accessibility for those who are color blind (and for some with low vision), they in no way solve the problem for users who are blind and are therefore dependent on tactile or auditory differentiation of status information.

Applicable Guidelines:
Section 508 - 1194.25(g), 1194.31(a)
Section 255 - 1193.41(c)