Fixed spelling colour => color

Not a real error, but many frowns at mixing British and US English, so I thought it's better to keep it consistent US English, especially since color is also a common keyword.

docs/api/objects/Points.html

@@ -51,7 +51,7 @@
 		<h3>[property:Material material]</h3>
 		<div>
 			An instance of [page:Material], defining the object's appearance.
-			Default is a [page:PointsMaterial] with a random colour.
+			Default is a [page:PointsMaterial] with a random color.
 		</div>