Can we change the color of a Storyline Character's outfit?

The more accurate way would be to use Replace Color. 

Hit W to use the Wand Tool and select the shirt. You might need to Shft-Click to add darker parts, but once it's selected, you'll see the dancing ants.

After you've made the selection for the area that you want to replace, Click Image>Adjustments>Replace Color.

The whole shirt should be selected. Double-Click the color box above "Result", this will bring up the color selection window. You will be able to manually enter the RGB color if you want, which is what I suggest since it's the most accurate way to get the color you want.

Here's the important part - You'll notice that all the gradients have disappeared and there's now only a solid color. Above the Layers, you'll see Blending Modes (to the left of Opacity, it should default to "Normal"). Change it to Overlay or any of the other blend modes until you find the one you like. Voila! (I really hate Photoshop sometimes)