Colloring HTML elements depending on what action is called

Hi fellows. I'm requiring a suggestion, a hand, since can't solve this.
What I'm trying to do is this:

I have 2 actions by a controller. There's an active layout for
both(application.html.erb). There's two HTML elements defined in the
layout which I want to be collored diferently if one action is called or
the another. I suspect that can be done with Javascript, but must be an
easy way. What I though is that when I call one of the actions, it must
render a specific CSS file, which overwrite the style of the HTML
elements, giving to them the color I want, but....I can't give with it,
can't get it work correctly. Can you give me a clue about what should I
do, I've been around this a whole day.

Why not just define CSS classes for the two styles in a common
style sheet and set an instance variable in the controller to pass to
the view? e.g.

  <div class="<%= @actionclass %>"> ... </div>

I can imagine other approaches, but that seems simplest.

FWIW,

Yes Hassan that's a big better solution than the JS one, you opened my
mind, I appreciate it, thanks. Still I'm open to receive other
suggestions of ways to do this, for the sake of learn.