This is one of my favorite usability stories which I may have initially told in a different post, but it applies here. When I started word processing graduate school papers in the early 80's, I used a Commodore 64; I had to buy the word processing program separately and had a Commodore floppy drive, which was used to load the program and then to save workfiles on a separate floppy disk.
Without thinking or reading the floppy disk manual (which I still have in some moving box), I had inserted my word processing software disk and was about to insert my data disk, when I read this warning: "DO NOT EJECT THE DISK WITH THE GREEN LIGHT SHOWING". The green light was a power indicator. The tech writer must have intended to say was not to eject the data disk while it was still being written to (probably a flicking amber light). There was also a warning against shutting down the drive with the disk in it. So did that mean my software disk was toast, caught between the devil and the deep blue sea? I quickly decided that the documentation was misleading; otherwise, the floppy drive was utterly unusable. Still, I held my breath the first time I ejected my software disk.
This is a big lesson in usability: the initial response to the human interface, including documentation, frames one's experience. And for me, that includes indicator lights. I once remember being the DBA/system administrator behind the National Archives' milrecs application. There had been no transition with my predecessor but I soon saw an amber light on the server hosting the data warehouse. I was confident that this was problematic; researching the issue, I learned that one of the disks was dead on the RAID-5 device. In essence, this is like driving your car with your spare tire; you need to replace the tire ASAP or your vehicle becomes inoperable. If another disk pops, your RAID storage becomes unusable.
One of the things that first-time users need to know is how to process the indicator statuses; what do different colors mean, what about flickering indicators, etc.? To what extent are they consistent from other experiences? For example, my cellphone displays red while in the process of charging; I also see a red indicator when the cellphone is running low on battery. What happens when a battery is fully charged? Does the indicator go out? Do I need to guard against overcharging?
To a certain extent, we may have other experience contexts, e.g., traffic lights: green go, red stop, yellow warning. To the extent we may infer from other contexts, the light choices may be more natural.
When I got my Gooloo power bank, the instructions really didn't address my initial learning experience. I do know that often with battery-operating devices using rechargeable batteries, including laptops or cellphones, one often must initially charge the unit before using it (unplugged). What I initially experienced was a blinking blue light, vs. say a steady red light in charging my cellphone. Blinking might be an indicator meaning an error condition or charging in process. There is a discussion buried in the documentation of multiple indicator lights on the top of the devices which indicate 4 stages of charging (when the stage is complete, its color turns steady) and when fully charged, the lights go off. Charging is done by USB, which you can interface with household current with the use of an adapter (which you can buy with $5 at Walmart), which I use all the time for charging my cellphone. In this case, I didn't know the context of using a blue light; maybe it was signifying a problem with a charging process. It does explain elsewhere it might take 15 minutes to charge in a car or up to 2-3 hours via USB connection to household electricity. My issue is that this information should occur at the start of the document vs. the reader having to comb through the document.
