herb
葒 refers to a type of herb, specifically a plant used in traditional contexts. The meaning is narrow and botanical, without clear abstract extensions.
葒 combines the grass radical 艹 with 紅, which likely contributes a phonetic element. The exact historical development is uncertain.
The grass radical 艹 sits above 紅, suggesting a red-tinged herb. Picture a field of herbs with reddish stems or flowers.
For コウ, imagine a gardener saying 'I'll grow this herb in a cold frame': 'cold' -> コウ, and the herb thrives under the grass-like cover.