Apply the Color Expression control to easily change the fill color of multiple layers. For example, apply the Color Control effect to a shape layer. Set an expression for its fill property and then pickwhip to the Color Control. When you change the color in the effect control panel, the shape’s fill will change accordingly.

Say that you have a second layer that you always wanted to be the same color as the first layer. First, lock the effects control panel for layer one so that it stays there when layer two is selected. Then, go to the second layer’s fill property and create an expression. Next, pickwhip to the Color Control of the layer one effect. Now, when the Color Control color value is changed, both layers will have the change applied.

See a quick example here: