Use of Color
Colors are an important consideration when designing a high performance HMI. Gray-scale colors are used instead of the traditional bright red, green, and blue colors.
The person that designs the HMI must understand the diverse audience that may view the HMI. For example, an operator may look at a motor on a traditional HMI. If it the HMI has colored the motor green, the operator may conclude that the motor is running. However, if a maintenance technician looks at the same motor, he may conclude that the motor is not faulted. These are logical conclusions. They reflect the respective interest of the person viewing the HMI where the operator wants the motor to run and the maintenance technician wants it to be working.
In reality, the motor is simply "scheduled" to run, meaning when it runs depends on its control mechanism. For example, the motor may run when there is product on the line or boxes on the conveyor. In other words, the motor may be periodically starting and stopping automatically.
A high performance HMI can eliminate this confusion by introducing a color that signifies a state of "scheduled." A common high performance HMI practice is to use a dark gray to signify a "scheduled" state for equipment. This color should never compete with more alerting colors that "pop" from the HMI resulting in the viewer's eye's being drawn to the portion of the HMI where the problem may be occurring.