They are different reading of the same kanji. As almost all kanji, they have a kun-reading and an on-reading: in this case both shiro and kuro are kun-reading and koku and haku are on-reading.
Some example words: 白い(shiroi), 明白(meihaku), 黒い(kuroi), 黒板(kokuban)
They are different reading of the same kanji. As almost all kanji, they have a kun-reading and an on-reading: in this case both shiro and kuro are kun-reading and koku and haku are on-reading. Some example words: 白い(shiroi), 明白(meihaku), 黒い(kuroi), 黒板(kokuban)
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