Full Idea
The proposition that nothing is red and green all over at once is not analytic, but it is rationally graspable, so it seems to be an a priori synthetic proposition.
Gist of Idea
Red and green being exclusive colours seems to be rationally graspable but not analytic
Source
Robert Audi (Epistemology: contemporary introduction [1998], IV p.100)
Book Reference
Audi,Robert: 'Epistemology: a contemporary introduction' [Routledge 1998], p.100