Reference selector CSS

I want to change the styling of a refence selector with css, but cannot find where to do it (like height of the box, coloring etc). Please let me know where I can find the css / sass files to change   See below screen part, We want to achieve that the height of the text field (Code) is the same as the reference selecto.
1 answers

Hi Andre,

I think that the following webpage can help you out:!/MyFirstModule/How_to_customize.

EDIT: This link guides you into Using SASS with Mendix.