Needs some UX input, we can do better here even by stealing the styling from the in-app settings.
It is not just a visual problem but interaction one: is very difficult to open the value selector
I am doing a bunch of work on these screens for Bug #832269 which should be landing soon. Taking.
As a part of bug #832269 we enlarged the dropdown and placed it inside of a .button.icon-dialog building block. Please test the new UI on the add/modify event screen as it should be much easier to use. Thanks! Bug #832269 landed in master in: https://github.com/mozilla-b2g/gaia/commit/4a19eb0c1b1ab1d72d082ab45415c56577a725a3