You don't. You sign and then it will ask for a donation, which you don't have to pay.
I'm not going to defend some of their choices of cover model (urgh #20), but if you think this model is darker-skinned than #30 or #10's model, you might need to adjust your screen. But the point isn't to compare this model to past models so much as to the contents of the books, where Marco is described as having darker features, a trait which is underrepresented as protagonists in children's media.
But yeah, YMMV. I'm not going to browbeat anyone into signing.