Emacs Version 24.2 (9.0)
MacOSX SnowLeopard 10.6.8

From my understanding, Emacs24 has the build-in theme functionality.
but after Emacs is booted up, I cannot change the theme as I want it to.

For the initial setup, I put 

  (load-theme 'tango-dark t)

then the first screenshot shows the Emacs window.
After that, I implement M-x load-theme dark-blue
the second screenshot is what the result looks like.  The result appears slightly different but not entirely.

It seems like "the first loaded theme cannot be overridden".

Can anyone guess what the problem is?

soichi