I made an edit or two to my original comment, so just to make sure you see it: Your "Bookmark" button conveys very clearly what it is for and what it will do w

I made an edit or two to my original comment, so just to make sure you see it: Your "Bookmark" button conveys very clearly what it is for and what it will do when I click on it. "Bookmark" is a verb and "Bookmarked" is a status. So what about "Complete" for the greyed-out label and "Completed" for the green state? That would similarly make the deactivated button show an "Action" word—the exact action that will happen when I click it—and the activated state a "Status" word (that I can intuitively return to its original status by clicking again).