Adjusting size of product variant dropdown box

I like the way product variant and quantity appears on my individual product pages on mobile (see attachment), but it looks different on desktop (also attached).

I would like the dropdown box and its text (circled on attachment) to display larger (both text and box) on desktop, so there's less of a difference between the sizes of the quantity input box and variant box. I'm also not sure why the arrows show as blue on desktop. Is it possible to change the color?

I very much appreciate any suggestions!

(Sample page: https://hettieroberts.com/canvas-art-prints/aglow )