A solid white Lesser Pied prolly makes the whitest snake (nothing whiter than Pied white), as does a solid white BlkEL. Most BELs develop some mild yellow striping. My Lesser Mojo boy was about 700g before I sold him, and he had a faint dorsal stripe.
I agree with Jinx on the best ways to hit the whitest of whites; either a white LesserPied or one of the BlkEL types that generates solid whites, like the Lemonback