Here’s a cool way to swap Stylesheets on the fly using UDASSS(Unobtrusive Degradable Ajax Style Sheet Switcher). Works great even if Javascript is disabled on the browser.

The Unobtrusive Degradable Ajax Style Sheet Switcher combines the power of Server Side processing and DOM scripting to swap style sheets on the fly with the power of Ajax. If JavaScript is disabled - UDASSS degrades gracefully to improve your website accessibility. Needless to say, it is very sexy indeed.
Link: UDASSS Official Documentation