Comment 1 for bug 165865

A really ugly emergency workaround:
1 - select the marked item
2 - in the XML editor,
    - look for its <style> attribute, there'll be a marker-*
tag with the
      tag's name
    - look (under <defs>) for the item <marker> whose tag
"id" matches
      the tag name; it should have a subitem <path>; edit
the latter's
      "style" attribute, adding a "fill" tag with your color
of choice
   - go back to the marked item, change the marker-* tag
with something
     else, then to the original marker name, so Inkscape
repaints the
     item

YMMV. This is a very poor hack, since all users of that
marker will
have it with the same color - also, I bet it won't load when the
developers fix the bug.