From wikipedia "Kohl has been worn traditionally as far back as the Bronze age (3500 B.C. onward) by the Egyptian queens". Looking through my stash I found a few different brands of black eyeliners so I decided to swatch them to see if there was really a difference in colour between them.
Swatches of black eyeliners on NC42 skin
1- Lacome's Le Crayon Khol
2- MUFE aqua eyes in 0L
3- Urban Decay 24/7 pencil in Zero
4- MAC Kohl power eye pencil in Feline
5- Prestige Waterproof eyeliner in Black
6- Urban Decay 24/7 pencil in Oil Slick
7- NYX Jumbo eyeshadow pencil in Black Bean
Verdict: Definite colour differences in the intensity of black. Feline which is supposedly the "blackest black" wins the same title in my stash (I read Stila's Black Onyx wears better than Feline but I don't own it so can't make a comparison). Prestige Waterproof eyeliner in Black is surprising darker than both MUFE and UD which I did not expect.
Overall wear: My eyes are quite watery and I under no circumstances can wear a eyeliner that is not waterproof. I prefer UD Zero to MUFE 0L as it lasts longer on my waterline with far less smudges. Oil slick is great for lining the upper lash on night's out when I feel like a bit of sparkle :). Surprisingly, Feline lasts fairly long on my waterline and even though the difference in intensity in quite subtle in the swatches in real life I feel my eyes stand out more with Feline. Lancome's Kohl was one of my first black eyeliner's but I don't reach for it very often (if at all) as being a kohl it smudges very easily on me.
Personal winners: UD Zero and MAC Feline would be enough to fulfill my black eyeliner needs.The former for my waterline and the latter for smudgy smokey dark intense eyes.