PromucFlow_constructor/app/client/src/theme/defaultTheme.css

.appsmith-light-theme {
  /* Syntax of style naming */
  /* --appsmith-<entity name>-<style-name> */
  /* --------------------- */

  /* input */
  --appsmith-input-focus-border-color: var(--appsmith-color-black-900);

  /* search input */
  --appsmith-search-input-focus-mobile-border-color: var(--appsmith-color-black-900);
  --appsmith-search-input-mobile-border-color: var(--appsmith-color-black-400); 

}