How long should you wait to dye your hair if you have just shampooed it?

You should be alright to dye your hair at the minimum of an hour later, that lets all the "ingredients" from your shampoo to soak in even if you wash it out. The reason to do this is that the shampoo is still working as a "cleaner" for about an hour after you wash your hair, so if you were to put dye in it, it would just wash away.