How can you tell.....?

[ROACH]

Just a short question.

If you were to breed a Pastel Het Piebald with a Spider you can get this:

25%	1/4	Normal
25%	1/4	Spider
25%	1/4	Het. Piebald
25%	1/4	Spider Het. Piebald

Now my question is this:
If 25% is Spider and 25% is Spider Het. Piebald how can you tell wich ones are the Hets? Sames goes for the normals?