AE progress bar color change

Quick answer：

In Adobe After Effects (AE), changing the color of a progress bar involves using expressions and keyframing. You can apply an expression to the 'Color' property of the layer representing the progress bar to dynamically change its color. This can be done by using the expression 'thisComp.layer('Layer Name').effect('Effect Name').property' and adjusting the color values. Additionally, keyframing can be used to create smooth transitions between different colors.