Full Idea
Perhaps 'grue' has causal features, but only derivatively, in virtue of its relation to green.
Gist of Idea
'Grue' only has causal features because of its relation to green
Source
Sydney Shoemaker (Causal and Metaphysical Necessity [1998], III)
Book Reference
Shoemaker,Sydney: 'Identity, Cause and Mind' [OUP 2003], p.413
A Reaction
I take grue to be a behaviour, and not a property at all. The problem only arises because the notion of a 'property' became too lax. Presumably Shoemaker should also mention blue in his account.