What makes a color feel 'children's book'?

I’ve been staring at a palette for a new manuscript, and something’s off. The colors are technically right—bright, saturated—but they don’t land. It’s like the green isn’t green enough to be a forest, or the blue doesn’t hold the weight of sky. I keep thinking: is it about hue? Saturation? Or is it something deeper—like how a child might feel the color, not just see it? What do you remember about the first time a color in a book made you believe in it?