diff --git a/NEWS b/NEWS
index 9f4f3c85d..d7c9ded5a 100644
--- a/NEWS
+++ b/NEWS
@@ -53,6 +53,13 @@ New in spot 1.99.5a (not yet released)
     with spot.product() or spot.product_or() and in the shell with
     autfilt's --product or --product-or options.
 
+  * The print_dot() function supports a new option, +N, where N is a
+    positive integer that will be added to all set numbers in the
+    output.  This is convenient when displaying two automata before
+    building their product: use +N to shift the displayed sets of the
+    second automaton by the number of acceptance sets N of the first
+    one.
+
   * Renamings:
     is_guarantee_automaton() -> is_terminal_automaton()
     tgba_run -> twa_run
diff --git a/src/bin/common_aoutput.cc b/src/bin/common_aoutput.cc
index ac6ee52f1..811412e02 100644
--- a/src/bin/common_aoutput.cc
+++ b/src/bin/common_aoutput.cc
@@ -84,7 +84,7 @@ static const argp_option options[] =
   {
     /**************************************************/
     { nullptr, 0, nullptr, 0, "Output format:", 3 },
-    { "dot", OPT_DOT, "1|a|b|B|c|e|f(FONT)|h|n|N|o|r|R|s|t|v",
+    { "dot", OPT_DOT, "1|a|b|B|c|e|f(FONT)|h|n|N|o|r|R|s|t|v|+INT",
       OPTION_ARG_OPTIONAL,
       "GraphViz's format (default).  Add letters for "
       "(1) force numbered states, "
@@ -96,7 +96,8 @@ static const argp_option options[] =
       "(o) ordered transitions, "
       "(r) rainbow colors for acceptance sets, "
       "(R) color acceptance sets by Inf/Fin, (s) with SCCs, "
-      "(t) force transition-based acceptance.", 0 },
+      "(t) force transition-based acceptance, "
+      "(+INT) add INT to all set numbers", 0 },
     { "hoaf", 'H', "i|l|m|s|t|v", OPTION_ARG_OPTIONAL,
       "Output the automaton in HOA format.  Add letters to select "
       "(i) use implicit labels for complete deterministic automata, "
diff --git a/src/twaalgos/dot.cc b/src/twaalgos/dot.cc
index e9de09c3f..0910a120a 100644
--- a/src/twaalgos/dot.cc
+++ b/src/twaalgos/dot.cc
@@ -66,6 +66,7 @@ namespace spot
       bool opt_all_bullets = false;
       bool opt_numbered_trans = false;
       bool opt_want_state_names_ = true;
+      unsigned opt_shift_sets_ = 0;
       std::string opt_font_;
 
       const char* const palette9[9] =
@@ -112,6 +113,16 @@ namespace spot
 		  parse_opts(def.c_str());
 		break;
 	      }
+	    case '+':
+	      {
+		char* end;
+		opt_shift_sets_ = strtoul(options, &end, 10);
+		if (options == end)
+		  throw std::runtime_error
+		    ("missing number after '+' in print_dot() options");
+		options = end;
+		break;
+	      }
 	    case '1':
 	      opt_want_state_names_ = false;
 	      break;
@@ -189,6 +200,7 @@ namespace spot
       void
       output_set(std::ostream& os, int v) const
       {
+	v += opt_shift_sets_;
 	if (opt_bullet && (v >= 0) & (v <= MAX_BULLET))
 	  {
 	    static const char* const tab[MAX_BULLET + 1] = {
@@ -228,7 +240,7 @@ namespace spot
       html_set_color(int v) const
       {
 	if (opt_rainbow)
-	  return palette[v % palette_mod];
+	  return palette[(v + opt_shift_sets_) % palette_mod];
 	// Color according to Fin/Inf
 	if (inf_sets_.has(v))
 	  {
diff --git a/wrap/python/tests/automata.ipynb b/wrap/python/tests/automata.ipynb
index c576294be..74f0c9b08 100644
--- a/wrap/python/tests/automata.ipynb
+++ b/wrap/python/tests/automata.ipynb
@@ -177,7 +177,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faee805b4b0> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c25174540> >"
        ]
       }
      ],
@@ -569,7 +569,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faee8042780> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c2515b810> >"
        ]
       }
      ],
@@ -639,7 +639,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faee8042600> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c2515b690> >"
        ]
       }
      ],
@@ -715,7 +715,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faee8042660> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c2515b6f0> >"
        ]
       }
      ],
@@ -1175,7 +1175,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faee8042d80> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c2515be10> >"
        ]
       }
      ],
@@ -1276,7 +1276,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faee8042e40> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c2515bed0> >"
        ]
       }
      ],
@@ -1394,7 +1394,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faee80425a0> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c2515b630> >"
        ]
       }
      ],
@@ -1493,7 +1493,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faee8042630> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c2515b6c0> >"
        ]
       }
      ],
@@ -1963,7 +1963,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faee80423c0> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c2515b450> >"
        ]
       }
      ],
@@ -2578,7 +2578,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faee8042ed0> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c2515b840> >"
        ]
       }
      ],
@@ -2734,7 +2734,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faee80426c0> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c250f61e0> >"
        ]
       }
      ],
@@ -2804,7 +2804,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7faedb3750f0> >"
+        "<spot_impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f3c250f6150> >"
        ]
       }
      ],
@@ -2814,9 +2814,11 @@
      "cell_type": "code",
      "collapsed": false,
      "input": [
+      "# Using +1 in the display options is a convient way to shift the \n",
+      "# set numbers in the output, as an aid in reading the product.\n",
       "a1 = spot.translate('a W c'); display(a1.show('.bat'))\n",
-      "a2 = spot.translate('a U b'); display(a2.show('.bat'))\n",
-      "# the product should display pairs of states, unless asked not to\n",
+      "a2 = spot.translate('a U b'); display(a2.show('.bat+1'))\n",
+      "# the product should display pairs of states, unless asked not to (using 1).\n",
       "p = spot.product(a1, a2); display(p.show('.bat')); display(p.show('.bat1'))"
      ],
      "language": "python",
@@ -2886,7 +2888,7 @@
         "<title>G</title>\n",
         "<polygon fill=\"white\" points=\"-4,4 -4,-111 159,-111 159,4 -4,4\" stroke=\"none\"/>\n",
         "<text font-family=\"Lato\" font-size=\"14.00\" text-anchor=\"start\" x=\"56.5\" y=\"-92.8\">Inf(</text>\n",
-        "<text fill=\"#5da5da\" font-family=\"Lato\" font-size=\"14.00\" text-anchor=\"start\" x=\"78.5\" y=\"-92.8\">\u24ff</text>\n",
+        "<text fill=\"#f17cb0\" font-family=\"Lato\" font-size=\"14.00\" text-anchor=\"start\" x=\"78.5\" y=\"-92.8\">\u2776</text>\n",
         "<text font-family=\"Lato\" font-size=\"14.00\" text-anchor=\"start\" x=\"94.5\" y=\"-92.8\">)</text>\n",
         "<!-- I -->\n",
         "<!-- 1 -->\n",
@@ -2921,7 +2923,7 @@
         "<path d=\"M129.969,-34.6641C128.406,-44.625 130.75,-54 137,-54 141.688,-54 144.178,-48.7266 144.471,-41.8876\" fill=\"none\" stroke=\"black\"/>\n",
         "<polygon fill=\"black\" points=\"144.031,-34.6641 147.601,-41.4598 144.244,-38.1576 144.456,-41.6511 144.456,-41.6511 144.456,-41.6511 144.244,-38.1576 141.312,-41.8425 144.031,-34.6641 144.031,-34.6641\" stroke=\"black\"/>\n",
         "<text font-family=\"Lato\" font-size=\"14.00\" text-anchor=\"start\" x=\"132.5\" y=\"-72.8\">1</text>\n",
-        "<text fill=\"#5da5da\" font-family=\"Lato\" font-size=\"14.00\" text-anchor=\"start\" x=\"129\" y=\"-57.8\">\u24ff</text>\n",
+        "<text fill=\"#f17cb0\" font-family=\"Lato\" font-size=\"14.00\" text-anchor=\"start\" x=\"129\" y=\"-57.8\">\u2776</text>\n",
         "</g>\n",
         "</g>\n",
         "</svg>"