executing a random command

I am writing a function that will implement a random colour theme in emacs. Have a look at this example:

(defun random-colour-theme () ;; written 2017-04-02
  "Pick a random colour theme."
  (interactive)
  (setq randomNumber (random 2))
  (setq nameOfRandomColorTheme (nth randomNumber '(
"color-theme-xemacs"
"color-theme-xp")))
  (nameOfRandomColorTheme)
  )

The last part,

(nameOfRandomColorTheme)

, of course, doesn't work, even though either

(color-theme-xp)

or

(color-theme-xemacs)

work. How do I randomly pick one of these two commands and then execute it?

I don't know Emacs lisp so this may be off base, but:

  (setq nameOfRandomColorTheme (nth randomNumber '(
"color-theme-xemacs"
"color-theme-xp")))

is setting nameOfRandomColorTheme to a string value, and then:

  (nameOfRandomColorTheme)

is using that string as if it were a function.

In your example you say

(color-theme-xp)

as a function does what you want: perhaps you want a structure like:

(if (= 0 randomNumber) (color-theme-xemacs) (color-theme-xp))