I think young snakes are darker and more patterned with the yellow dorsal stripe, then they change color into the cream color with the light dorsal stripe as adults. I could be wrong, its hard to find any info on these guys, but that's what I've been able to gather based on pix of young snakes and their adult parents. Maybe someone will come along who knows for sure.

Have you seen a cream colored, patternless adult snake with a yellow dorsal stripe?