In many cultures, white is the traditional color for a wedding dress, but she chose to wear white for her graduation ceremony too.

white 的意思是"白色"，在西方文化中常象征纯洁、神圣和新的开始。 这里 white 指代"白色的衣服"，通过颜色来代表特定服装，这种用法在英语中很常见。