red
韎 centers on the color red, specifically a reddish dye or leather used in ancient contexts. Its meaning is narrow and tied to historical material culture.
韎 combines 韋 (tanned leather) with 末 (tip, end, powder), likely referring to a red dye or pigment applied to leather. The exact historical development is uncertain, but the character is associated with a specific reddish color used in ancient rituals or attire.
Picture tanned leather (韋) being dipped into a red powder (末) at the tip of a brush, turning it a vivid red. The combination of leather and red powder gives 韎 its meaning of red dye or red-colored leather.
For バイ, imagine buying (buy -> バイ) a piece of red leather at an ancient market. The red color of the leather reminds you of the reading バイ.