In December of 1978, the Environmental Protection Agency (EPA) proposed hazardous waste management standards that included reduced requirements for several types of large volume wastes.
Sometimes they have a black or olive-brown base color. Some have a lighter tan base color. As with most snakes, the belly is a lighter color, usually a yellowish cream color. Some specimens have lighter-colored bands running the length of their bodies. Refer to the king cobra pictures above.
Sheesh, great question. I've never heard anything suggesting that the color of snake venom is related to what's in it, so I suspect this is not the case, but I doubt that anyone's looked. All the snake venom I've ever seen has been that yellowish-amber color, but I don't know what gives it that color.