My experiences with using light-colored gels on white backgrounds have been more unfavorable than favorable. for whatever reasons. I've found that shooting gelled studio flash at white or cream-colored paper can easily lead to a lot of what I call "blowback", which is what you have in shot #1. Blowback is where the background light comes back to the subject and wraps around the sides of the head and or body...in this case, shot #1 has a strong yellow light outline. The second shot has eliminated/avoided that problem of blowback. I've had better luck using thunder gray paper when I want to make pastel-hued backgrounds. The gray reflects a lot less light than white, and for the lights I have, which do not dial down very low, the gray paper's end results are a lot less prone to what I call "color pollution", where a big sheet of white paper bounces colored light all over the shooting area, which is what I see here...her skin has a lot of color pollution in it, due to the gelled light spilling all over the shooting area.