/usr/lib/GNUstep/ColorPickers/StandardPicker.bundle/Resources/GSRGBColorPicker.tiff is in gnustep-gui-runtime 0.26.2-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/GNUstep/ColorPickers/StandardPicker.bundle/Resources/../../../../../share/GNUstep/ColorPickers/GSRGBColorPicker.tiff