As much as the original author bemoans having to do the labeling themselves, 99% of people don't care or don't have such a mix of cables as to make it a challenge to find one to suit the task.

If you care, then care enough to do small, practical things for yourself. A little loop of tape. Paint marker. Even just sorting them into drawers/boxes/whatevers by type.

I thought blue indicated USB 3.0?

E markers are required for USB3, so that’s why. If you have a cable capable of 100 or 240W, they will also have a marker (it’s required), even if they only do USB2 speeds.