When you select a new color of a location or transition, the undo action does not force a redraw for the location/transition to show the color change. However, the undo has taken place as witnessed by going to the declaration and then back to the template. How to trigger the bug: 1. Right click location/transition and select a new color 2. Click anywhere on the canvas to remove selection of location/transition 3. Undo using either Ctrl-Z or Edit->Undo 4. Witness that color didn't change back 5. Go to other template/declaration/system in the tree and back 6. Witness that color has indeed changed