Capture class extends PImage, so you can do just the same with a Capture object as with a PImage object:

http://processing.org/reference/PImage_mask_.html
http://processing.org/reference/tint_.html

F

// JMyron m; // = a camera object

// in draw():

m.update();//update the camera view
 int[] img = m.image(); //get the normal image of the camera

//draw what the camera sees
 loadPixels();
 for(int i=0;i<width*height;i++){
   pixels[i] = color( red(img[i]), green(img[i]), blue(img[i]), 127);
 }
 updatePixels();


or


pixels[i] = (127 << 24) + ( img[i] & 0xFFFFFF );  // 127 = alpha 50%


F