Hello! Here's only one way of many!
In order to avoid painting one, I found a suitable graphic online that was in the right perspective.
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In the graphics own document, I removed the background and then converted it to black and white.
I transferred the graphic document to the main image document by dragging and dropping with the Move Tool onto the main image doc's tab, I then converted it to a smart object.
I used Free Transform to resize and position the "paint spill" where I wanted it.
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I added a layer mask to the "paint spill" layer and masked out he ladder and the base with the Brush Tool.
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I then added a solid color fill adjustment layer and clipped it to the "paint spill" layer. I set it's blending mode "overlay".
I then chose the color of the paint I wanted the "paint spill" to be be by double clicking the solid color fill adjustment layer's thumbnail.
(Note: I have intentionally made this yellow)
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Done