init

src/slic3r/GUI/GUI_Utils.cpp

@@ -548,7 +548,7 @@ void RemoveButtonBorder(wxWindow* win)
     GtkCssProvider* provider = gtk_css_provider_new();
 
     const char* css =
-        "button {"
+        "button, button:hover, button:active, button:focus {"
         "  border: none;"
         "  outline: none;"
         "  box-shadow: none;"

src/slic3r/GUI/PresetComboBoxes.cpp

@@ -865,6 +865,9 @@ PlaterPresetComboBox::PlaterPresetComboBox(wxWindow *parent, Preset::Type preset
         clr_picker = new wxBitmapButton(parent, wxID_ANY, {}, wxDefaultPosition, wxSize(FromDIP(20), FromDIP(20)), wxBU_EXACTFIT | wxBU_AUTODRAW | wxBORDER_NONE);
         clr_picker->SetBackgroundColour(StateColor::darkModeColorFor(*wxWHITE));
         clr_picker->SetToolTip(_L("Click to select filament color"));
+        #ifdef __WXGTK__
+            RemoveButtonBorder(clr_picker);
+        #endif
         clr_picker->Bind(wxEVT_BUTTON, [this](wxCommandEvent& e) {
             // Check if it's an official filament
             auto fila_type = Preset::remove_suffix_modified(GetValue().ToUTF8().data());

src/slic3r/GUI/wxExtensions.cpp

@@ -1022,6 +1022,10 @@ ScalableButton::ScalableButton( wxWindow *          parent,
         m_width = size.x * 10 / em;
         m_height= size.y * 10 / em;
     }
+
+    #ifdef __WXGTK__
+        Slic3r::GUI::RemoveButtonBorder(this);
+    #endif
 }