The best is to make a new canvas and “play” there with the possibilities to see what you achieve what result, so you learn best to deal with it. In this right click menu you can make various settings, but they will be applied to the whole selected layer, so if there is already more than a single stroke on the layer, you would have to separate the stroke to be saved / preserved before and transfer it to its own layer.
Or way up in Layer Styles, you can also do many funny things, but less to color-manipulation Grab the circles with your mouse and move them to adjust the color, or, if you click directly on the curve, set new nodes you place to your needs (remove the nodes with the Delkey or pull them out of that window to remove unneeded nodes)
