Prima facia

Don’t judge a book by its cover. I attempted this recently by asking a nearby assistant for a ‘blue book’, she gave a quizzical glance and then asked ‘which hue’, I said I wasn’t certain but I knew geometrically that it was ‘round’. I thought this would narrow the range significantly; she turned and began rummaging through a large box and finally produced a blue ball. I guess I may have to stick to judging books superficially for the moment.