I have a bunch of Emacs color themes that I built a few years ago, they use the old color-theme.el system, I'd also adapted a web-based theme creator, so that it could load existing themes, as long as they were in a fixed format, the same as used by http://themes.sweyla.com/ - All in all I was quite invested in color-theme.el

I've begun to convert some of my regular themes over to the new (deftheme) format. The main advangatge is there's no reliance on color-theme.el anymore. There's a couple of small drawbacks, when a theme is first loaded, you need to confirm it, since it's possible to run arbitrary emacs-lisp in it. You then need to enable it for future use, so it's a quick trip to .emacs - This is only going to bug you if you run Emacs in -Q quick-start mode, which I do in some cases.

With Emacs 24 you can create a theme customize-create-theme it's ok, but not the best way to to it, it's much better to learn how to work with theme source code, which like everything that extends Emacs, is written in emacs lisp.

To that end, have a look at this base template, it's meant to serve as a guide, it'd be better to create a few yas/snippets.

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    ;;; Filename: name-theme.el 
(deftheme name
  "DOCSTRING")

;; Not a bad idea to define a palette...
(let (
      (color-1 "#ffffff")
      (color-2 "#ff0000")
      (color-3 "#00ff00")
      (color-4 "#0000ff"))

  ;; Set faces
  (custom-theme-set-faces
   'name ;; you must use the same theme name here...
   '(default ((t (:foreground ,color-1 :background black))))
   '(cursor  ((t (:background ,color-4))))
   '(fringe  ((t (:background ,color-3))))
       ;;; etc... 
       ;;; don't use these settings of course, 
       ;;; they're horrible.
   )

  ;; Set variables
  (custom-theme-set-variables
   'name ;; again specify the same theme name...
   '(any-variable EXPR)

   (provide-theme 'name)
    ;;; name-theme.el ends here

For more advanced examples, look at the new built in themes, I'd recommend tango-theme.el which you'll be able to find using, M-x describe-theme tango.

Have a look at my extensions to Drew Adams hexrgb.el for some useful color helpers, and don't forget the always helpful rainbow-mode.el. Personally I think Emacs plus these little extensions, are the best way to make themes.