diff --git a/nutils/_graph.py b/nutils/_graph.py
index 9a3b4fcb4..705e81da3 100644
--- a/nutils/_graph.py
+++ b/nutils/_graph.py
@@ -58,7 +58,7 @@ def generate_graphviz_source(self, *, fill_color: Optional[GraphvizColorCallback
         subgraph_children = _collect_subgraphs(self)
         id_gen = map(str, itertools.count())
         self._collect_graphviz_nodes_edges({}, id_gen, nodes, edges, None, fill_color)
-        return ''.join(itertools.chain(['digraph {bgcolor="darkgray";'], _generate_graphviz_subgraphs(subgraph_children, nodes, None, id_gen), edges, ['}']))
+        return ''.join(itertools.chain(['digraph {bgcolor="darkgray";'], _generate_graphviz_subgraphs(subgraph_children, nodes, None, id_gen, 0), edges, ['}']))
 
     def export_graphviz(self, *, fill_color: Optional[GraphvizColorCallback] = None, dot_path: str = 'dot', image_type: str = 'svg') -> None:
         src = self.generate_graphviz_source(fill_color=fill_color)
@@ -250,9 +250,9 @@ def _generate_asciitree_subgraphs(children: Mapping[Optional[Subgraph], Sequence
         yield from _generate_asciitree_subgraphs(children, id_gen_map, child, bridge+('├ ' if i else '└ '), bridge+('│ ' if i else '  '))
 
 
-def _generate_graphviz_subgraphs(children: Mapping[Optional[Subgraph], Sequence[Subgraph]], nodes: Mapping[Optional[Subgraph], Sequence[str]], subgraph: Optional[Subgraph], id_gen: Iterator[str]) -> Iterator[str]:
+def _generate_graphviz_subgraphs(children: Mapping[Optional[Subgraph], Sequence[Subgraph]], nodes: Mapping[Optional[Subgraph], Sequence[str]], subgraph: Optional[Subgraph], id_gen: Iterator[str], depth: int) -> Iterator[str]:
     for child in children[subgraph]:
-        yield 'subgraph cluster{} {{bgcolor="lightgray";color="none";'.format(next(id_gen))
-        yield from _generate_graphviz_subgraphs(children, nodes, child, id_gen)
+        yield 'subgraph cluster{} {{bgcolor="{}";color="none";'.format(next(id_gen), 'darkgray' if depth % 2 else 'lightgray')
+        yield from _generate_graphviz_subgraphs(children, nodes, child, id_gen, depth + 1)
         yield '}'
     yield from nodes.get(subgraph, ())
diff --git a/tests/test_graph.py b/tests/test_graph.py
index 64b0aed7f..89131a511 100644
--- a/tests/test_graph.py
+++ b/tests/test_graph.py
@@ -288,7 +288,7 @@ def test_multiple_graphviz_source(self):
                          'bgcolor="lightgray";'
                          'color="none";'
                          'subgraph cluster8 {'
-                         'bgcolor="lightgray";'
+                         'bgcolor="darkgray";'
                          'color="none";'
                          'subgraph cluster9 {'
                          'bgcolor="lightgray";'
@@ -299,7 +299,7 @@ def test_multiple_graphviz_source(self):
                          '4 [shape=box,label="f"];'
                          '}'
                          'subgraph cluster10 {'
-                         'bgcolor="lightgray";'
+                         'bgcolor="darkgray";'
                          'color="none";'
                          '6 [shape=box,label="g"];'
                          '}'