User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:51.0) Gecko/20100101 Firefox/51.0
Build ID: 20161027004020
Steps to reproduce:
3.1 Launch Firefox with a clean profile
3.2 Click menu [≡] → select Customize.
3.3 Drag the download button from the navigation bar and place it on the tabs bar.
3.4 Perform at least 3 downloads.
3.5 Open the Downloads Panel.
3.5 The downloads button's color does not remain the same. It changes from blue to black.
3.1 Firefox is successfully launched.
3.2 Customize mode is enabled.
3.3 The downloads button is placed on the tabs bar.
3.4 After the downloads are completed the downloads button turns blue.
3.5 The downloads button's color remains the same.
This issue is actually a feature, the color of the Download Panel button is supposed to turn blue as the download is finished and return to the default state as the user saw the notification.
Thank you for your efforts in the previous test day!