#+BEGIN_SRC emacs-lisp :eval never
  ;; setup
  (set-face-attribute 'org-block nil :background
                        (color-darken-name
                         (face-attribute 'default :background) 3))
  (defface org-block-R
    `((t (:background ,(color-lighten-name "#455EB3" 50))))
    "Face for R src blocks")
  (defface org-block-emacs-lisp
    `((t (:background ,(color-lighten-name "#7F5AB6" 30))))
    "Face for elisp src blocks")
  (defface org-block-python
    `((t (:background ,(color-lighten-name "#00FF00" 30))))
    "Face for python blocks")

#+END_SRC
#+BEGIN_SRC emacs-lisp :var x=1
  (defun x () 1 ) 
#+END_SRC

#+BEGIN_SRC R
  x <- function () 1
#+END_SRC
#+BEGIN_SRC python
  def x:
    return(1)
#+END_SRC

#+BEGIN_SRC shell
echo 1
#+END_SRC