Using arraybuffer changes colors of image

The issue is that when you create a 4 bit graphics, I believe it maps the colors values right through - but when you draw the image, 4 bits is treated as the Mac color palette.

The easiest thing to do is to supply a palette when drawing your 4 bit buffer:

let buf = Graphics.createArrayBuffer(120, 120, 4, {msb:true});
let bufimg = {
  with:120, height:120, bpp:4, palette = new Uint16Array([...]), buffer:buf.buffer
}

g.drawImage(
  bufimg,
  0,
  0,
  {scale: 2}
);

and that might sort you out...