Full Idea
A property-instance must be spread out in space, or it is not clear how a colour nature can be present, but then it has to be a complex entity, and tropes are supposed to be simple entities.
Gist of Idea
A colour-trope cannot be simple (as required), because it is spread in space, and so it is complex
Source
J.P. Moreland (Universals [2001], Ch.3)
Book Reference
Moreland,J.P.: 'Universals' [Acumen 2001], p.65
A Reaction
Seems a fair point. Nothing else in reality can be sharply distinguished, so why should 'simple' and 'complex'?