diff --git a/crates/engine/src/clip_ops_tests.rs b/crates/engine/src/clip_ops_tests.rs
--- a/crates/engine/src/clip_ops_tests.rs
+++ b/crates/engine/src/clip_ops_tests.rs
@@ -1161,3 +1161,15 @@ fn applied_transform_centres_its_points_in_the_clip_picture() {
         assert_eq!(m.param("position").unwrap().value.as_vec2().unwrap(), frame_centre);
     }
 }
+
+#[test]
+fn set_param_rejects_colour_component_that_overflows_f32() {
+    // 1e300 is a finite JSON number but saturates to an infinite f32, which saved as `null` and could not be reopened
+    let mut s = demo();
+    let a = v1(&s)[0].clone();
+    s.execute("effects.apply", json!({"clips": [a.id.0], "effect": "tint"})).unwrap();
+    let r = s.execute("effects.setParam", json!({"clip": a.id.0, "effect": "tint", "param": "black", "value": [1e300, 0, 0, 1]}));
+    assert!(r.is_err(), "an overflowing colour component must be refused");
+    let bytes = filmcraft_format::encode(&s.project, false);
+    filmcraft_format::decode(&bytes).unwrap();
+}
diff --git a/crates/engine/src/commands.rs b/crates/engine/src/commands.rs
--- a/crates/engine/src/commands.rs
+++ b/crates/engine/src/commands.rs
@@ -3814,12 +3814,19 @@ pub(crate) fn json_to_param(template: &ParamValue, v: &Value) -> Option<ParamVal
         }
         ParamValue::Color(_) => match v {
             Value::String(s) => ParamValue::Color(filmcraft_color::parse_hex(s)?),
-            Value::Array(a) => ParamValue::Color([
-                a.first()?.as_f64()? as f32,
-                a.get(1)?.as_f64()? as f32,
-                a.get(2)?.as_f64()? as f32,
-                a.get(3).and_then(Value::as_f64).unwrap_or(1.0) as f32,
-            ]),
+            Value::Array(a) => {
+                let c = [
+                    a.first()?.as_f64()? as f32,
+                    a.get(1)?.as_f64()? as f32,
+                    a.get(2)?.as_f64()? as f32,
+                    a.get(3).and_then(Value::as_f64).unwrap_or(1.0) as f32,
+                ];
+                // a finite f64 such as 1e300 saturates to an infinite f32, which a saved project cannot reload
+                if !c.iter().all(|x| x.is_finite()) {
+                    return None;
+                }
+                ParamValue::Color(c)
+            }
             _ => return None,
         },
         ParamValue::Bool(_) => ParamValue::Bool(v.as_bool()?),