The Dianshi Clickable Highlighter retracts at a press, so the chisel tip is ready whenever your hand is. It writes in a soft, deep blue that underlines a single line or covers a whole passage, depending on how you hold it. The body is frosted and translucent with a pale blue clip, and pressing either the top or the clip itself retracts the tip, so you can put it away with one hand.
Click it open and mark the page. Because the tip retracts fully, the highlighter can ride in a pen loop or loose in a bag without marking anything around it. Keep it clipped to your planner, and color-coding stays one click away.