Ethan loves water. Water of any kind, really; in a cup, in a hose, in a sink, it doesn't matter. He wants it, and he wants it yesterday.
He especially loves taking baths and showers, and would prefer to stay in there for hours if he could. Unfortunately, he also has two tendencies that limit his bath time: a tendency towards patches of eczema on his legs, and a tendency to splash and/or pour water all over the bathroom floor. He just wants to share the water with everyone, I guess!
Every couple of baths or so, we like to use colored bath fizzers or food coloring to add a little splash to his water adventure. So don't worry, that yellow water is by design, not by accident. And his expression is because he likes to splash, but doesn't like water in his eyes. His solution? Splash, scream, and squish your eyes shut as tightly as possible, and not necessarily in that order.