Apple undertook a comprehensive redesign of the OS X Yosemite operating system : the interface has been significantly redrawn. Now the OS has a sleek design, translucent panels, avoiding gradients and iOS textures is clearly visible in the desktop platform, and looks much more modern. Icons in OS X 10.10 also unchanged OS X 10.9: they got new minimalistic design and a flat.
To learn how to change the default icons in the new OS X, later in this article.
How to change the application icons on the Mac:
Step 1: Download the new application icon, for example, the icon for the iTunes-style OS X Yosemite can be found here.
Step 2: In the Finder, go to the Applications folder and select the application for which you want to replace the icon.
Step 3: Right-click and select Properties.
Step 4: Drag the downloaded icon on the first step on the icon in the Properties window, as shown in the screenshot below. Alternatively, you can copy the image to the clipboard, select the icon in the properties window and make a paste.
Step 5: Enter the administrator password.
Step 6: Log off or restart the Dock. To do this, run the Terminal, copy command “killall Dock” (without the quote) and press Enter.
To return to the old icon again, select the application in the Applications folder and open its properties. Highlight the icon in the properties window and press Backspace.