It's a literal translation of a Zappa song, which also includes "that", and is meant to be somewhat vernicular. In the English version I think the implication is that the child has been told about yellow snow before. So it's "that yellow snow we talked about before, remember?"
Even leaving aside the obscure song reference, this is exactly what I’d say to my kid when we are on top of a mountain and he is eating snow and I see a yellow patch. “Itu/that” is obviously in the sentence to allow reference to a particular patch of snow.