How to change Bootstrap input form (placeholder) styles?

Question

css

Good day.
Plz tell me how you can set your own styles for input forms from Bootstrap?
For example, change the color of the border and remove rounding from the forms.
bootstrap-3.ru/css.php#forms
UPD. In the course of editing, there was a gag with editing placehorder. The methods described in this article do not work.

Answer 1

For example like this? jsfiddle.net/3wrksapq/2