Config git-gutter with linum in Spacemacs

spacemacs-git-gutter-with-linum.el

(defun dotspacemacs/layers ()
  (setq-default
   dotspacemacs-configuration-layers
   '((version-control :variables
                      version-control-global-margin t
                      version-control-diff-tool 'git-gutter
                      ))))


(defun dotspacemacs/init ()
  (setq-default
   ;; Enable global line-numbers
   dotspacemacs-line-numbers 'relative
   ))


(defun dotspacemacs/user-config ()
  (progn
    ;; Linum

    ;; NOTE: the "relative" flag for "dotspacemacs-line-numbers 'relative"
    ;; doesn't seem to be working, so we add the hooks here manually
    (when (eq dotspacemacs-line-numbers 'relative)
      (add-hook 'prog-mode-hook 'linum-relative-mode)
      (add-hook 'text-mode-hook 'linum-relative-mode))

    (setq-default
     linum-format "%4d \u2502"
     linum-relative-format "%4s \u2502"
     ))

  (progn
    ;; Git Gutter
    (set-face-attribute
     'git-gutter:added nil :background nil :foreground "green")
    (set-face-attribute
     'git-gutter:deleted nil :background nil :foreground "red")
    (set-face-attribute
     'git-gutter:modified nil :background nil :foreground "blue")

    (setq-default
     git-gutter:modified-sign "!"
    ))
  )

What is the face you use to have the current line with a grayed-out yellow? I like it, thanks for this btw, it worked like a charm