Ah, OK I see what's going on now. So two things;
- what you're seeing are edges marked (assigned) a 'property', in this instance that's "Sharp", it tints edges with the property that blue-ish-green-ish colour. It can be ignored for now as it doesn't affect the edit-ability of the mesh (it's pre-assigned to the mesh for convenience).
2) the dots
(vertices) - they are there, just not immediately visible because they're being obscured by all the other on-screen elements. If you right-click
near any one of the corners they select and highlight (become more apparent). Or you can press "A
" to select the entire mesh and it will highlight as indicated at that point in the video - the fact that they are not highlighted just means they are not selected for manipulation or modification.
The discolouration indicates a property assignment to an edge, "Sharp" in this instance.