In a Merge node, what is the yellow input used for?

• A. Foreground input
• B. Alpha input
• C. Background input
• D. Mask input

Answer: (C)

In a Merge node, you compose two images by layering an overlay (foreground) on a base (background) using an optional mask. The yellow input is the background—the image that serves as the canvas for the composite. The foreground goes into the blue input and sits on top, while the green input can carry a mask to control where the overlay appears. This ordering matters: using a different port for the background changes which image becomes the base and which is the overlay.