glitter, gleam, twinkle
煌 centers on bright, sparkling light: glittering, gleaming, or twinkling. It describes a vivid, eye-catching shine.
煌 combines 火 (fire) with 皇, which likely contributes the sound and carries a sense of brilliance or sovereign radiance. Together they express bright, glittering light.
Fire 火 beside an emperor-like 皇 radiance: imagine a royal crown blazing with glittering flames, each jewel twinkling brightly.
For コウ, picture a glittering crown (皇) glowing with fire (火): crown -> コウ, and the whole scene gleams.