Morpho butterflies are well known for their brilliant blue color that has a low angular dependence. This distinctive coloration has long been attributed to the skillful combination of order and disorder in the hierarchical nanostructures, which allows the interference of light to avoid iridescence. However, there remains a fundamental mystery: the artificial Morpho-blue color is successfully obtained despite the lack of vertical randomness. Using a numerical simulation, we found that the three-dimensional randomness can be converted to a two-dimensional randomness. This finding leads to a novel approach for the simple nanofabrication of not only Morpho-blue but also of more general photonic devices.