Pad centered video, but with different top, bottom colors?

Resizing then padding a centered video, maintaining aspect ratio, to a final 720 x 1280, with the same top an bottom colors, say darkgray, is below, which I think I got from Stack Overflow or somewhere (it works).

• scale=720:1280:flags=spline:force_original_aspect_ratio=decrease:eval=frame,pad=720:1280:-1:-1:eval=frame:color=darkgray

But I would like to have different colors for top and bottom paddings. See the example pic below, which I want. Thanks in advance.