How can I change the aqua theme in Yosemite?

How can I change the aqua theme/skin to a dark one in Yosemite? I'm referring to the window title bars, scroll bars, buttons, etc (the cocoa aqua ui theme?). Everything is grayish by default, but i'd like a dark theme.


Solution 1:

If you're still looking for a method to darken your UI in Yosemite, download Flavours 2 and choose the "Smooth Criminal" flavour. Here's a quick screenshot of "Smooth Criminal."

Flavours 2 is still in Beta, but most things look great with this skin.

Solution 2:

You can change the Finder icons with LiteIcon, freeware.

More icons than you could ever need at DeviantArt

Alfred (freeware) can do custom theming, but might require the Powerpack (not free) for what you require.

There's also ThemePark