Should users be allowed to adjust the colors of graphic elements in an information presentation? If so, how freely?

One of the most basic guidelines for color usage is that color should be used sparingly, for particular purposes. The colors in a good design have been chosen, hopefully by trained and experienced experts, to comply with numerous constraints. This suggests that users--typically not trained and experienced color experts--should not be allowed to change the assigned colors.

On the other hand there are good arguments for allowing users some ability to adjust the displayed colors. Changes in the viewing environment can affect the usability of the presentation. The instrument panels in automobiles are a good example--the daytime display is inappropriate for the viewing conditions at night, and the brightness levels of the night display are often adjustable. In some workplaces the colors may vary from monitor to monitor. Users new to a job may need context information displayed more prominently than more experienced users. Finally, one can argue that users should have as much freedom to adapt their working environment to their own styles as is consistent with safe, efficient operations.

In aviation operations users often have some ability to vary the colors of displayed graphic elements. In some cockpits display colors are adjusted by software to adapt to changing ambient illumination. In Air Traffic Management users can change the brightnesses of some graphic elements singly or in groups, and some information presentation is designed local to the facility.

There are a few general guidelines about user adjustments, for example:

8.6.2.9.1 User preferences. When appropriate to the functionality of an application, users should have the option of selecting from a variety of color sets as a user preference setting for aspects of an application that do not involve coding or status.
8.6.2.9.2 Easy return to default color scheme. When users are allowed to change color settings of aspects of an application that do not involve coding, the application shall provide an easy way to restore the default color scheme.
8.6.2.9.4 Coding and status colors. When different users will share a computer monitor, individual users shall not be able to change colors for coding and status of facilities, services, or equipment such as alarms or alerts.
8.6.2.9.5 Range of color contrast. When users are allowed to adjust the color and contrast settings, a variety of color selections capable of producing a range of contrast levels shall be provided.

FAA Human Factors Design Standard http://hf.tc.faa.gov/hfds/

There are also a few guidelines relating to automatic brightness adjustment hardware and software in cockpit displays, but we know of no guidelines that address in detail the constraints on user adjustments of colors that are required in order to preserve the important aspects of the designers' work. We are developing guidelines for what color adjustments users can be allowed to make and what aspects of the color design must be invariant to user adjustments, in the context of various work environments.