GripHelper

 var gridXZ = new THREE.GridHelper(100, 1);
 gridXZ.position.set(10,0,10);
 scene.add(gridXZ);

 //grid xy
 var gridXY = new THREE.GridHelper(5, 1);
 gridXY.rotation.x = Math.PI/2;
 gridXY.position.set(5,5,0);
 gridXY.setColors( new THREE.Color(0xff0000), new THREE.Color(0xffffff) );
 scene.add(gridXY);

 //grid yz
 var gridYZ = new THREE.GridHelper(2, 0.5);
 gridYZ.position.set( 0,2,2 );
 gridYZ.rotation.z = Math.PI/2;
 gridYZ.setColors( new THREE.Color(0xffffff), new THREE.Color(0x00ff00) );
 scene.add(gridYZ);