You can change the color of notes for each cannel by editing *.ini files.
Please check following section of the user manual.
> 7. How to customize
> (2) View Mode Configuration
> (c) Color
> Ch-xx-NoteRGBA Color of the piano roll bar at each channel.(RGBA)
If you want to change the color of notes for each scale,
please check following thread, and download special version of MIDITrail.
[#64066] request
http://sourceforge.jp/forum/forum.php?thread_id=32269&forum_id=23361
Reply to #69230