muk_web/muk_web_theme/static/src/views/form/form.scss

.o_form_view {
    &:not(.o_field_highlight) .o_field_widget:not(.o_field_invalid) .o_input:not(:hover):not(:focus) {
    	border-color: $gray-200 !important;
    }
	.o_required_modifier.o_field_widget:not(.o_field_invalid) .o_input:not(:hover):not(:focus) {
		border-color: $gray-600 !important;
	}
}