Color Blindness, SCADA and HMI
Written by Neal Babcock
When you are designing an HMI or a SCADA display, you have to consider color blindness.
Approximately 5% to 8% of men and 0.5% of women are born colorblind. Usually, these people are protans (red weak) and deutans (green weak). Though there are varying degrees of color blindness, there are some that cannot differentiate red from green, so the colors look the same to them.
These people negotiate stoplights based on the position of the light that is on, not the color.
This is a big problem in industry, where red and green are commonly used to indicate the status of a piece of equipment.
There are a couple of ways to solve this problem. We could use icons that have different shapes, depending on whether they are on or off. In addition to being a different color, a pump icon that is off could have a round hole cut out in the middle, such as is shown below.
Here is what the pumps shown above might look like to a person who is colorblind.
The black dot in the middle of the pump that is off will be appreciated.
Another option is to add text. Not only does this help the person who might be colorblind, it obviously confirms the state of the equipment to those even with true color vision.
An interesting benefit to keeping the icons discernible to the color blind is that these icons are easier to read for those of us who are not color blind.
Excerpted from How to Program RSView32
This article is incredibly irresponsible. You state the statistical occurrence of color blindness but don’t mention that there are levels of severity amidst those who are afflicted that range from almost unnoticeable to monochromacy.
I am color blind, and it is information such as this that makes my life much harder than it has to be. I can see your red and green switches perfectly well. I can tell the difference between red and green indicator lights. But if any future employer within earshot hears me mention that I am color blind, I may be automatically disqualified because he read an article off some website that lumped all people with color-blindness into one group, and that group sees only grays.
Thanks a lot.
Alex,
You are correct – the original post did not state that there are varying degrees of color blindness. I assumed that to be common knowledge. Still, I have corrected that omission.
I certainly don’t intend to make your life harder. I simply wanted to help HMI designers create more legible displays.
I recently worked with the owner of an engineering firm. He couldn’t tell me if the LED on the processor was red or green, yet he managed to get by. In fact, he inspired me to write the post.
I would hope that a potential employer would not judge you solely on your color blindness. That would be rather shallow of him.
Best of luck to you,
Neal