I am also having similar issue. ...I even extracted a logo from a properly working GCD with RGN, then used GIR to load that image to another GCD, and when that GCD is loaded, the GPSr image is not correct.
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EDIT: To try and be more clear, changing boot.bin logo using GIR and RGN always results in the correct image on the device, however the quality is greatly diminished, and the color palette is completely wrong, even when using unedited images extracted from firmwares that do not exhibit this behavior.... Thus, something is wrong with either GIR (v58), RGN (v94), or both.