It appears when the "Apply" button on the Compare & Apply page is highlighted (meaning that two or more locations are selected) but the cursor is not hovering over the "Apply" button, the button appears half in grey and half in blue. Here is a screenshot:
It appears when the "Apply" button on the Compare & Apply page is highlighted (meaning that two or more locations are selected) but the cursor is not hovering over the "Apply" button, the button appears half in grey and half in blue. Here is a screenshot: