Hi there, I was hoping to see a screenshot to check whether an unread notification might be causing this issue, or if it is something else. Here's what I mean:
When you first get a "like" notification, the orange star pops up like this: http://cl.ly/image/1q0v3p0L110K
When you click on the star, you see a list of your notifications. Your new, unread notifications will have a blue dot next to them, like this: http://cl.ly/image/1W0l1P3A3q3V
If you close the notification list at this point, the orange star may appear again. This is because the new notifications are still considered to be unread. If you click on an unread notification (one with a blue dot next to it), you will see more detail about that notification: http://cl.ly/image/0w1f0N2C1C0W
This marks the notification as read. If you open your notification list again, you'll see that the blue dot next to it has gone away: http://cl.ly/image/3e393U1O2t3j
As long as none of the notifications in that list have blue dots next to them, the notification icon should stay grey. Can you check to see if you have any unread notifications in your list?