An interesting, probably slicker approach... but I wonder if there may be something like a 'refresh' of the palette required?

As it stands, I don't think I'm dealing with a 'palette-ed' image here:-

c:\> ffprobe -hide_banner ruddy.png
Input #0, png_pipe, from 'ruddy.png':
  Duration: N/A, bitrate: N/A
  Stream #0:0: Video: png, rgb24(pc), 320x234, 25 fps, 25 tbr, 25 tbn

c:\> mediainfo ruddy.png
General
Complete name                            : ruddy.png
Format                                   : PNG
Format/Info                              : Portable Network Graphic
File size                                : 84.9 KiB

Image
Format                                   : PNG
Format/Info                              : Portable Network Graphic
Width                                    : 320 pixels
Height                                   : 234 pixels
Bit depth                                : 24 bits
Compression mode                         : Lossless
Stream size                              : 84.9 KiB (100%)
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