I do not know of a preference to set the default BoxPlotSeq to have Box Type("Outlier") which sets the color to Black, or how to change the default BoxPlotSeg line color. Maybe a JMP developer has a JSL-Only preference that can do this.
Note that GraphBuilder boxplots by default are black.
The attached file is an add-in created from the script below. If you install the add-in, then once you create your boxplots, run it from Main Menu > Add-Ins > BlackBoxPlot.
You might want to postpone installing the add-in, in case there are other solutions that can set the default; then this add-in is unnecessary.
JSL scripters, with a little additional scripting, using Pick Color(), or a menu to prompt for color, line width, fill and transparency, would allow be a nice app to customize all boxplots. Note this script was written to run on JMP 13 and 14.
Names Default To Here(1);
winlst = Window();
For(i=1, i<=nitems(winlst), i++,
_nme = winlst[i] << Get Window Title;
_child = winlst[i] << Child;
If( (_child << class name) == "ListBox",
_clnme = _child[OutlineBox(1)] <<get title;
If( contains(_nme, "Oneway") |
contains( _clnme, "Oneway") |
contains( _clnme, "Fit Group")
,
bseg = _child << Xpath("//BoxPlotSeg");
if(nitems(bseg)>0, bseg << Set Line Color("Black") )//Set Box Type("Outlier"))
);
);
);