How to Change the Icons of Programs Pinned to the Taskbar
Goto
%appdata%/Microsoft/Internet Explorer/Quick Launch/User Pinned/Taskbar
Right click on the program of the icon you want to change and change the icon.
Go back to the pinned programs folder and click on the shortcut with the newly changed icon.
Hit Ctrl+X (cut).
Navigate to your desktop and hit Ctrl+V (paste).
Right click the program on the taskbar (with the old icon), and from the options that pop up, click Unpin this program from taskbar.
Drag the shortcut (with the new icon) from your desktop, to the taskbar.
Have Fun