Closer but can't figure out how to select the RGB Channel on it's own.

// =======================================================
var image = app.activeDocument;
var background = app.activeDocument.artLayers.getByName("Background");
background.duplicate();
background.visible = false;
var copy = image.artLayers.getByName("Background copy");

var newLayer = image.artLayers.add();
var newLayer = image.artLayers.add();

var Layer1 = image.artLayers.getByName("Layer 1");
var Layer2 = image.artLayers.getByName("Layer 2");

image.activeLayer = copy;

var redChannel = image.channels.getByName("Red");
var arrayRed = new Array (redChannel);
image.activeChannels = arrayRed;
image.selection.selectAll();
image.selection.copy();
image.activeLayer = Layer1;
image.paste();

var greenChannel = image.channels.getByName("Green");
var arrayGreen = new Array (greenChannel);
image.activeChannels = arrayGreen;
image.selection.selectAll();
image.selection.copy();
image.activeLayer = Layer2;
image.paste();
image.activeLayer.blendMode = BlendMode.SCREEN;
Layer2.opacity = 50;

copy.visible = false;
image.mergeVisibleLayers();
image.selection.selectAll();
image.selection.copy();

copy.visible = true;
image.activeLayer = copy;

var redChannel = image.channels.getByName("Red");
var arrayRed = new Array (redChannel);
image.activeChannels = arrayRed;
image.paste();

var greenChannel = image.channels.getByName("Green");
var arrayGreen = new Array (greenChannel);
image.activeChannels = arrayGreen;
image.paste();

var RGBChannel = image.channels.getByName("RGB");
image.activeChannels = arrayRGB;