diff --git a/src/app/mod.rs b/src/app/mod.rs
index bb6af37b3..31fc33a10 100644
--- a/src/app/mod.rs
+++ b/src/app/mod.rs
@@ -1435,6 +1435,10 @@ pub enum Message {
     PropAttrCommit(String),
     /// Toggle the inline color picker dropdown open/closed.
     PropColorPickerToggle,
+    /// Collapse the inline color picker dropdown. Fired when another
+    /// properties-panel dropdown (a combo_box) opens, so at most one panel
+    /// dropdown is open at a time and they can't overlap. (#235)
+    PropColorPickerClose,
     /// Toggle the full ACI colour palette expansion.
     PropColorPaletteToggle,
     /// Enter the model-space editing mode inside the given viewport (MSPACE).
diff --git a/src/app/update/mod.rs b/src/app/update/mod.rs
index 137794324..6153a6d6f 100644
--- a/src/app/update/mod.rs
+++ b/src/app/update/mod.rs
@@ -2123,6 +2123,13 @@ impl OpenCADStudio {
                 Task::none()
             }
 
+            Message::PropColorPickerClose => {
+                let i = self.active_tab;
+                self.tabs[i].properties.color_picker_open = false;
+                self.tabs[i].properties.color_palette_open = false;
+                Task::none()
+            }
+
             Message::PropColorPaletteToggle => {
                 self.tabs[self.active_tab].properties.color_palette_open =
                     !self.tabs[self.active_tab].properties.color_palette_open;
diff --git a/src/ui/properties.rs b/src/ui/properties.rs
index c37efebf1..f553fa985 100644
--- a/src/ui/properties.rs
+++ b/src/ui/properties.rs
@@ -207,6 +207,7 @@ impl PropertiesPanel {
             .size(FONT_SZ)
             .padding([2, 6])
             .input_style(combo_input_style)
+            .on_open(Message::PropColorPickerClose)
             .width(Length::Fill)
             .into()
         };
@@ -387,6 +388,7 @@ impl PropertiesPanel {
             right: 6.0,
         })
         .input_style(combo_input_style)
+        .on_open(Message::PropColorPickerClose)
         .width(Length::Fill);
 
         prop_row_widget(label, combo.into())
@@ -489,6 +491,7 @@ impl PropertiesPanel {
             right: 6.0,
         })
         .input_style(combo_input_style)
+        .on_open(Message::PropColorPickerClose)
         .width(Length::Fill);
 
         prop_row_widget(label, combo.into())
@@ -509,6 +512,7 @@ impl PropertiesPanel {
             right: 6.0,
         })
         .input_style(combo_input_style)
+        .on_open(Message::PropColorPickerClose)
         .width(Length::Fill);
 
         prop_row_widget(label, combo.into())
@@ -542,6 +546,7 @@ impl PropertiesPanel {
             right: 6.0,
         })
         .input_style(combo_input_style)
+        .on_open(Message::PropColorPickerClose)
         .width(Length::Fill);
 
         prop_row_widget(label, combo.into())
@@ -574,6 +579,7 @@ impl PropertiesPanel {
             right: 6.0,
         })
         .input_style(combo_input_style)
+        .on_open(Message::PropColorPickerClose)
         .width(Length::Fill);
 
         prop_row_widget(label, combo.into())
@@ -655,6 +661,7 @@ impl PropertiesPanel {
             right: 6.0,
         })
         .input_style(combo_input_style)
+        .on_open(Message::PropColorPickerClose)
         .width(Length::Fill);
 
         prop_row_widget(label, combo.into())