looking for such a file or how to create a such file

thanks

Find an image with the heraldic colours you want and open it in Inkscape. Draw some rectangles and use the Dropper tool to fill them with colours frm your reference image.

A web search for "Inkscape custom colour palette" yields many results. Here's just one.
https://inkscape-manuals.readthedocs.io/en/latest/palette.html