Changing default view for Access 2016

Question

Hi all,  I just upgraded to Access 2016 from 2010.   When I open a form it has a different appearance - the control box is white instead of the light blue I'm so used to and the border is very, very thin so that it is hard to grab it and resize the form.   I don't see how to change these back to the old default - can anyone help me?   What I've tried so far: in the search box I typed themes and a bunch of different colored samples came up.   I clicked on one and nothing changed; I've tried it a couple of times.   I also entered 'colors' and got about the same result.  I also went to the 'account' in the left hand main menu and the one box says background, which I really don't care about, and the other box says themes and I tried both options, but nothing changes.  I must be looking in the wrong place; can you help me?   Thanks,  Gil