Sorry, i somehow forgot to answer this one...i tried your test project but i somehow fail to see the issue. Just remove the call to setTransparencyMode() and you'll get default transparency (not additive, which is obviously not what you want). jPCT takes care of making the black areas transparent by default. If you want more control, you can use
paint.setColor(Color.argb(255, 0, 50, 0));
...
canvas.drawARGB(0, 0, 0, 0);
...
Texture texture = new Texture(charImage, true);
instead, but in this case the outcome will be the same. But maybe i haven't fully understood the problem here. A commented screen shot might help in that case.