brilliantly colored veined stone
碭 centers on a stone with striking, colorful veins or patterns, making it visually brilliant.
碭 combines 石 (stone) with 昜, which likely contributes the sound and may relate to brightness or radiance, fitting the meaning of a brilliantly colored stone.
The left side 石 is a stone, and the right side 昜 looks like a sun 日 shining over a decorated surface. Imagine a stone with bright, colorful veins catching the sunlight.
For トウ, picture a brilliantly veined stone used as a toe ring: toe -> トウ, and the stone's colors shine on your toe.