As someone who has been in the electronic manufacturing business for some fourteen years, I know a thing or two about wiring. Now, I’m in no way an expert on bomb-making or explosives, but when it comes to knowing which wire to cut when diffusing bombs in movies, I have to call shenanigans on the whole point of tension surrounding those situations. Namely, knowing which wire to cut, and which wire not to cut.
Long story short, unless it’s an overly simplistic device I’m pretty confident you can’t ever tell which wire to cut by its color. There’s really no way to know just by the color alone what the wire does. You need an understanding of the device itself. On some level there are industry standards when it comes to wiring. In a very loose sense, yellow wires imply a certain voltage range, orange another, and so forth. Black or green is generally ground, and white is usually reserved for signal transmission, or some other special utility. Of course, all of this goes out the window when you’re talking about wiring DC versus AC. They’re not at all the same.
This would all be well and good if those standards meant anything. Most high-end products aren’t meant to be worked on, repaired, or tinkered with by anyone other than whoever made it, so you never really need to consider keeping some sort of wiring standard outside of your company. What one company follows may be completely opposite from what any other company does. Except for some generalities, anything goes.
Sow what does this all mean for those tense scenes where someone is trying to diffuse a bomb before all hell breaks loose? Basically, you can never just say “cut the blue wire”, or “don’t cut the yellow wire”. Whoever made that bomb is most likely a terrorist, or some other nefarious individual. Why the heck would they follow any sort of wiring standard, if one even existed? First off, if they’re just building a bomb off the cuff, they probably wouldn’t even be aware of such as standard. They’d most likely be using whatever wire they could scrounge, so the idea of them going out to get a spool of red 22 gauge wire doesn’t seem likely.
But let’s say that they are highly skilled and know exactly what they’re doing. Why would they follow a standard that the good guys could use to easily diffuse the bomb? That makes absolutely no sense! Even if your bomb is made in a top-secret lab by highly trained individuals, wouldn’t the evil mastermind direct his underlings to make it as unusual and as confusing to others as possible?
Though completely unreal, it can be chalked up to writers not knowing anything about wiring, but I suspect it’s part of the larger, pervasive issue of most plot devices being far too simplified than they would be in real life. Anyway, if you’ve made it this far, thanks for sticking with my rant!