is it possible to show everything in black? I cannot find a setting for this. I do not mind the different colors for input (so do not want to start editing all the colors to black).
If you're editing a multi-voice score, you can set all notes to black, across all layers, by doing the following:
a) Turn off the switch labeled 'Highlight Voice', or
b) Open 'Voice Colors' to modify the active layer's notehead color. This will present a list of options other than the default green. Check on the highlighted option, corresponding to black:
This option is a bit more sophisticated than option (a) in that the noteheads will give an indication of which voice/layer is currently active, since only the active layer will be non-semitransparent.
I hope this answers your question.