horse with a bluish white color
驄 centers on a specific horse coat color: a bluish white or dappled gray horse. The meaning is narrow and concrete, referring to this particular equine appearance.
驄 combines 馬 (horse) with 悤, which likely contributes the sound and may relate to the color idea, though the exact historical development of 悤 in this context is uncertain.
The left side is a horse 馬, and the right side 悤 looks like a complex pattern of lines and a heart. Imagine a horse with a bluish white coat that looks like a delicate, intricate pattern painted on its body.
For ソウ, picture a horse with a bluish white coat galloping through a field of 草 (そう, grass): the grass sways as the horse runs, and 草 -> ソウ helps you remember the reading.