"使发乳白光" can be translated as "to emit a milky-white light" or "to produce a milky-white glow" in English, depending on the specific context and intended nuance.
"Emit a milky-white light" emphasizes the action of sending out or radiating the light.
"Produce a milky-white glow" focuses more on the result or effect of creating a soft, whitish light.