Which color seebaby stroller is nice for boy? For qq3 , yellow, blue, purple and green , which one nicer?

Colour is more of a personal/adult thing, children wouldn't mind what colour their items are - but I'd recommend neutral colours like yellow, purple or green so the stroller can be given to anyone after that (given the fact that most parents still prefer a certain colour over the other based on gender). You probably would also want to consider what colour would be less common so you won't lose it (esp if you go to big baby events/gatherings) and which colour would be easier to clean/hide stains :x