What Visual Kei truly is...

[MR. Potato]

where is my bike?

[odoroboujohn]

It's on your head.

[kyogasuki]

"Visual Kei" as far as appearance go seems to be given to any band that dresses out of the "norm".  This could be anything from XJapan's wild style to the more well-known an.cafe's "omg i am a rainbow!" style.  When it comes to the style of music, you really can't listen to an artist and say "yeah, they are VK" since their musical styles vary greatly (again, XJapan and an.cafe as examples).  I think it is more of a label for a band...the kind of label that once you get, you are stuck with it lol.  Think about Dir en grey -- they started out with some crazy outfits (random: I love kyo's look for macabre!) but as time progressed, they faded out of it.  Now they are dressing (it appears) in whatever they pull out of their closet that morning.  Yet, many people will still (and probably always will) classify them as a VK band.

If I went through my music collection (400+ artists) and labeled them as either VK or not VK (based on what fans and biographies describe them as), 99% would get that label. 

Final conclusion:  It is a label given based on a band's clothing/makeup/hair style, and not the music they play.