Try this CSS which should override all other styles:
#gform_wrapper_2 input.ginput_total {
background-color: #FFF!important;
color: #000!important;
font-size: 150%!important;
font-weight: bold!important;
}
Screenshot of that applied to your form: Screenshot on 2023-11-09 at 12-26-54.png - Droplr
That is targeted to form 2 only. If you want to apply to the total field in all forms, change the first line to this:
.gform_wrapper input.ginput_total {
You can add this CSS to your theme (or child theme) stylesheet or via the Appearance Customizer (Appearance → Customize → Additional CSS)
See also this article for additional information about placing CSS snippets: https://docs.gravityforms.com/where-to-put-your-custom-css/