Docs: AmbientLight hint as suggested by @WestLangley. Closes #2872.

docs/api/lights/AmbientLight.html

@@ -18,7 +18,7 @@
 
 		<h2>Example</h2>
 
-<code>var light = new THREE.AmbientLight( 0xff0000 );
+<code>var light = new THREE.AmbientLight( 0x404040 ); // soft white light
 scene.add( light );</code>
 
 		will light objects with red.