If it is in the assembly that the lines, dots, sketches appear in black, the color put on the instance of the part must be removed and put on the part but not in the context of the assembly.
Edit: as soon as you change the graphic property of a part instance in an assembly, the wireframe elements and sketches appear in black, there are no options to avoid this phenomenon, (it's very unpleasant especially if you use a dark background color, black on dark blue is not great). if we put the color on the part out of the context of the assembly it's OK.
So if I summarize, you have to put the colors at the level of the parts and not the instances.
I had to change their colors via the instance and not via the part of the part and in the context of assembly hence my concern.
However, how can I now go back to remove the black color from the geometric elements? and that the colors that I define at the level of my parts appear well.