diff -r 5f45c28da2b5 src/DLD-FUNCTIONS/fltk_backend.cc
--- a/src/DLD-FUNCTIONS/fltk_backend.cc	Fri Oct 09 15:37:16 2009 +0200
+++ b/src/DLD-FUNCTIONS/fltk_backend.cc	Sat Oct 10 20:16:43 2009 +0200
@@ -146,7 +146,17 @@
 
     glLineWidth (1);
     glBegin (GL_POLYGON);
-    glColor4f (0,0,0,0.1);
+    glColor4f (0.45, 0.62, 0.81, 0.1);
+    glVertex2d (zoom_box(0), h () - zoom_box(1));
+    glVertex2d (zoom_box(0), h () - zoom_box(3));
+    glVertex2d (zoom_box(2), h () - zoom_box(3));
+    glVertex2d (zoom_box(2), h () - zoom_box(1));
+    glVertex2d (zoom_box(0), h () - zoom_box(1));
+    glEnd ();
+
+    glLineWidth (1.5);
+    glBegin (GL_LINE_LOOP);
+    glColor4f (0.45, 0.62, 0.81, 0.9);
     glVertex2d (zoom_box(0), h () - zoom_box(1));
     glVertex2d (zoom_box(0), h () - zoom_box(3));
     glVertex2d (zoom_box(2), h () - zoom_box(3));