I admit, I get a wee bit frustrated when trying to remember which cord goes in which slot for all my tech items. If you're nodding your head in jaded agreement, here's what to do about it.
It's so easy, it's ridiculous. Coordinate the colour and the design, and draw each of the same on the plug-in component and next to the plug-in site. Lines, dots, hearts -- whatever strikes your fancy. If you've got mad art skills and a little extra time, perhaps you could design very tiny cartoons that work together.
If you're looking for a little less permanent option than a Sharpie, try coloured tape, or even matching stickers. (Red, blue and gold stars, perhaps?)
And with the time we'll all save, let's give some extra applause to the Imgur poster's dad who "needs help logging into his email," but sure wins big in the analogue hack category.