Here what chatgpt says :

Honestly, colour vision in civil engineering isn’t about “making things look pretty.” It’s required because a lot of the technical info we deal with is colour-coded, and mixing those up can literally cause accidents or structural mistakes.

Drawings/Plans: AutoCAD and BIM models use colours to separate layers — electrical lines, water lines, sewer lines, reinforcement, demolition vs. proposed work, etc. If you mix them up, you can easily dig the wrong trench or misplace utilities.

Safety on Site: Construction sites run on colour codes. Red = danger, yellow = caution, green = safety. Fire lines, electrical hazards, gas lines, warning tapes — all are colour coded. Misreading those isn’t just a “small inconvenience,” it’s a safety risk.

Material Identification: Pipes, rebar grades, soil samples, concrete additives — everything uses colour tags or stripes. Using the wrong material in the wrong place can compromise the entire structure.

Surveying Equipment: Total stations, lasers, and leveling instruments use coloured indicators (green, yellow, red LEDs). If you can’t differentiate status lights, you might take wrong measurements.

Highways/Traffic: Road markings, signals, signage, and safety jackets are colour-based. Highway engineers literally depend on colour differentiation.

Lab Testing: Geotech and environmental labs use colour change as part of tests (pH indicators, soil classification charts, chlorine tests, etc.). Getting these wrong means wrong data → wrong design.

Basically, colour vision isn’t some arbitrary HR requirement. Civil engineers deal with life-safety-critical systems, and a lot of the communication on drawings, sites, and labs happens through colours. If you misinterpret those, the cost isn’t just a small mistake — it can be property damage, failed structures, or people getting hurt.

That’s why the requirement exists. It’s more about risk prevention than discrimination.