The button colors are all the same, and so they all fail. The only button with color is the 'hang up' button and thats big and red and invites you click it.
Answer button should be green. If I am muted, make that red, not just add 6 pixels of a line that is not noticeable.
Call UI has been defined elsewhere - just copy it. This 'shades of purple everywhere' UI is making me (and many others) as users have to think too much.
