Extrude preview: a New Body has its own colour, apart from Join (#1805) (#1861)

Thanks @DuBearte.

assets/styles/ui/palettes.rs

@@ -48,6 +48,7 @@ impl Tokens {
             body_edge: Color32::from_rgb(40, 44, 52),
             manipulator: Color32::from_rgb(40, 110, 220),
             preview_add: Color32::from_rgb(112, 160, 226),
+            preview_new: Color32::from_rgb(240, 225, 105),
             preview_sketch: Color32::from_rgb(32, 190, 96),
             preview_cut: Color32::from_rgba_unmultiplied_const(232, 84, 44, 110),
             cube_face: Color32::from_rgb(236, 239, 244),