tan horse
騧 centers on a specific horse coat color: a tan or yellowish-brown horse. The meaning is narrow and concrete, with no clear abstract extensions.
騧 combines 馬 (horse) with 咼, which likely contributes the sound. The character was created to name a specific horse color.
The horse radical 馬 stands beside 咼, which looks a bit like a stylized saddle or marking. Picture a tan horse with a distinctive saddle-shaped patch: 騧 is that tan horse.
For カ, imagine a tan horse pulling a car: car -> カ, and the horse's coat is the color of sun-bleached wood.
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