fair, white, clear, discriminate
晳 centers on clarity and brightness that makes distinctions visible: something fair, white, or clear, and the act of discriminating or telling things apart by that light.
晳 combines 析 (split, divide) with 日 (sun), suggesting sunlight that separates things and makes them clear or distinct. The exact historical development is uncertain, but the component relationship is consistent with the meaning of clarity and discrimination.
The sun 日 shines down after something is split apart 析, making everything fair, white, and clear so you can discriminate details.
For セキ, imagine a section of a forest being cleared by sunlight: section -> セキ, and the light makes everything fair and distinct.