Dark Edges?
I have created separate layers with the rectangle tool, filled with color, and used the multiply setting for the image. I'm wondering how to get rid of the dark edges that look like a black line around the rectangles of color blocking. They are not overlapping, because even when I drag the rectangle much farther down there is still a dark edge.
I'm new to PS and have tried to find answers, but I'm so new I don't even know how to look it up. Any help is appreciated! 
