Headcanon that Percy’s eyes change color to match the nearest major body of water. His eyes becoming murky near the Hudson and the East River. His eyes clear as crystal in the Mediterranean. His eyes getting white-ish flecks when the waves are rough. His eyes becoming dark when a storm rages on the sea. His eyes being an entrancing, misty green with gold and reddish flecks at sunrise. Imagine Annbeth freaking out when his eyes become a dull gray/green in the Cocytus.