It wasn't 'wrong' for me. i had a Subaru XT that whenever that light came on it stalled and refused to start up again. but again that was before OBDII came out which allows a car to run perfectly fine it's entire life even with the 'Service Engine Soon' light on. i know my age is showing but i remember back when the 'Engine/Check Engine/Engine Malfunction' light was a replacement for the Oil/Alt/Temp gauges on old cars in the late 1970s. that was when they made one lamp to take the place of three others. it was EFI that later made the 'Check Engine' lamp more of a 'Waste $50 just to figure out what's wrong with it!' light.
But that's off topic so i'll stop at that.
All the CECB's i see have lights that change color when on or off. blue for on, red for off, green for on, amber/red for off. it is designed to allow the user to know it's plugged in and in 'standby' mode. i really don't have trouble sleeping with it on the red/amber as it's so soft glowing, but green/bright digital blue (what is it with all new stuff having bright blue power lights?) keeps me awake. looks like HAL 9000 is staring at me or something.