My first thought was to move the color out of the TRACE, which is
really a view object. However we can't make signals a first-class
citizen either, because they change depending on what the current
simulation tab is and so (for instance) we can only load in the
workbook signals for the current tab. Hours later I backed it all
out and arrived at this simpler, less "correct" solution.
Fixes https://gitlab.com/kicad/code/kicad/-/issues/14231