diff --git a/src/graphviz.rs b/src/graphviz.rs
index c0ce9cf..7e62ed5 100644
--- a/src/graphviz.rs
+++ b/src/graphviz.rs
@@ -34,8 +34,8 @@ impl EGraph {
     }
 
     fn to_graphviz(&self) -> Graph {
-        // 1. Group nodes by typ and class
-        let mut class_nodes = std::collections::HashMap::new();
+        // 1. Group nodes by type and class (use BTreeMap to keep sorted so colors are consistent)
+        let mut class_nodes = std::collections::BTreeMap::new();
         //  and create mapping from each node ID to its class
         let mut node_to_class = std::collections::HashMap::new();
         for (node_id, node) in &self.nodes {
@@ -81,7 +81,7 @@ impl EGraph {
         let mut typ_colors = std::collections::HashMap::new();
 
         for (typ, class_to_node) in class_nodes {
-            let next_color = typ_colors.len() % N_COLORS + INITIAL_COLOR;
+            let next_color = (typ_colors.len() + INITIAL_COLOR) % N_COLORS;
             let color = typ_colors.entry(typ).or_insert(next_color);
             stmts.push(stmt!(attr!("fillcolor", color)));
             for (class_id, nodes) in class_to_node {