Red, yellow, green or gray: colors should clarify process conditions, not simply decorate a screen.
A good HMI does not aim to be the most colorful. It aims to be understood quickly.
During my internship at Agro Juice Processing, designing SCADA screens made me think about how clearly operating states and controls are presented. Too many colors can distract from what really matters.
A color is useful only when its meaning is consistent across the interface and understood by operators. Labels, shapes and contrast are also essential: critical information must never depend on color alone.
A few design principles
Reserve red for conditions requiring particular attention, in line with site conventions.
Use yellow or orange for warnings without creating unnecessary visual alarms.
Use neutral backgrounds and sufficient contrast for routine information.
Test screens with their future users, including under actual lighting conditions.
My key takeaway: consistent colors, clear information hierarchy and testing with operators matter more than a visually spectacular screen.
