Hello,
You can adjust the style of the +/- buttons by navigating to:
Theme Settings > Styles and Colors > Forms
Here, you will find options to modify:
Form fields style – Adjust the appearance of input fields.
Form border width – Control the thickness of form borders.
Form text & background color – Change the color of the buttons and input fields.
https://ibb.co/nsW4Df4S
If you want to change the style to only quantity form then let me know I will check and provide custom css.
Best Regards,
.
