dye made from red soil, ochre
雘 centers on a specific red pigment: a dye or ochre made from red soil. Its meaning is narrow and concrete, referring to the material itself.
雘 combines 丹 (cinnabar, red pigment) with 蒦, which likely contributes the sound. The character is specialized for a red dye or ochre.
The left side 丹 is a red pigment, and the right side 蒦 looks like a complex container. Imagine a pot of red soil being processed into a rich dye.
For ワク, picture a worker stirring a wok full of red ochre: wok -> ワク, and the red dye swirls inside.