Actually, BOTH explanations are correct. In some lighting conditions, it is difficult to see if the engine is windmilling, so the stripe on the hub shows that it is spinning.
On the other hand, ANA found that, by drawing one large and one small "eye" on their hubs, they reduced the percentage of bird ingestions dramatically, over just the stripe. Therefore, it serves BOTH purposes.
Freight Dogs Anonymous - O.O.T.S.K.
DAMN! This SUCKS! I just had to go to the next higher age bracket in my profile! :-(