"source contains no colors" despite following the instructions to import palette

[gnuimpcub]

Thank you so much for these detailed informations. What I wealth of possibilities I never knew of! Considering that I not only are learing these new aspects of Gimp but also are learning how to handle my new Wacom Intuos graphic tablet I will resort to this coloring technique, for the time being:

Convert an RGB picture to indexed, import the color palette, and use this palette with similar RGB pictures to create. 256 colors are more than enough for the beginning.