Change color elements of quantity selector on product pages
Example:

Code for Pipeline 5:
/* -- code start -- */
/* background color and text color */
.js-qty .js-qty__num { background-color: #333333; color:#ffffff;}
/* border around the quantity selector box */
.js-qty .js-qty__num {border-color: #333333;}
/* color for the + and - options */
.js-qty .js-qty__adjust { color: #ffffff;}
/* hover color for the + and - options */
.js-qty .js-qty__adjust:hover {color: #cc0000;}
/* - end - */
Code for earlier theme versions:
/* -- code start -- */
// background color and text color
.js-qty input[type="text"] { background-color: #333333; color:#ffffff;}
// color for the + and - options
.js-qty button { color: #ffffff;}
// border around the quantity selector box
.js-qty input {border-color: #333333;}
// hover color for the + and - options
.js-qty__adjust:hover {color: #cc0000;}
/* - end - */
For a bolder version of the text and selectors:

Use this version instead for Pipeline 5:
/* -- code start -- */
/* background color and text color */
.js-qty .js-qty__num { background-color: #333333; color:#ffffff; font-weight: bold;}
/* border around the quantity selector box */
.js-qty .js-qty__num {border-color: #333333;}
/* color for the + and - options */
.js-qty .js-qty__adjust { color: #ffffff;}
/* hover color for the + and - options */
.js-qty .js-qty__adjust:hover {color: #cc0000;}
/* - end - */
Use this version instead for earlier theme versions:
/* -- code start quantity -- */
.js-qty input[type="text"] { background-color: #333333; color:#ffffff; font-weight: bold;}
.js-qty button { color: #ffffff; font-weight: bold;}
.js-qty input {border-color: #333333;}
.js-qty__adjust:hover {color: #cc0000;}
/* - end - */
hex color code references:
http://www.colorhexa.com/web-safe-colors
https://picular.co/
Where do I add the code?
Use this link to learn where exactly to add this code snippet: