How to customize paper-select component?

I need to customize paper-elements like paper-select and paper-select with search, but don't really know is it possible and if so how exactly to do it.

I tried this https://ember-power-select.com/docs/styles/, but doesn't work (yes, we have scss). I tried the same example as on the link and instead of a blue border it created a grey one. And for sure this grey border isn't related to the

$ember-power-select-border-color: #64A5ED;

selector in app.scss, because the same grey border appears for this import along:

@import 'ember-power-select';

without any selectors at all. One of the task is to move placeholder from center to the left corner of the input. But ::placeholder { flex: left } does not work. Also I don't have strong computer science background, so I would highly appreciate if you explain this as simple as possible.