magcolo said:
That's just lazy talking, it's like saying "while some skirts are "definitely" overskirt, it's not worth hassle, so let's move them all to showgirl skirt". There're tons of "hassles" on the site, if everyone thinks like this, guess how many tags will be left. If you think it's not worth the hassle, fair, you won't ever be forced to do the gardening, but don't use it as an excuse to nuke a legitimate concept.
I don't see how your example describes a situation similar to the reasoning I gave. A type of skirt doesn't change depending on the lighting, the color calibration of the uploader's monitor or even how good their eyes can distinguish color.
Meanwhile, the wiki for aqua hair even mentions how many factors can change the appearance of the hair, leading to overlap with blue hair and green hair. Having a tag with inherent overlap with another, potentially incompatible tag doesn't sound ideal, and would lead to either constant gardening or continued misue.