Ok, I am going to assume you have 2.0. But I have 1.9 ObjectDock Plus.
You say OD is on your taskbar, so this means you pinned it there yourself.
Note: the System Tray is to the right with the clock this is NOT the taskbar even though it is on it.
If it is in the system tray you can’t change it, that I know of without an app. That can do it.
As for the one pinned to the taskbar you can’t change it either, so un-pin it
Go to the START MENU click on ALL PROGRAMS look for OBJECT DESKTOP or STARDOCK folder click on it.
Look for OBJECTDOCK right click on it then Hover over SEND TO then Click on DESKTOP (CREATE SHORTCUT)
Now that it’s on the desktop Right click on the Icon then click on PROPERTIES in the Properties dial log box click on
SHORTCUT tab at top then at the bottom click on CHANGE ICON (NOTE: you may get and error message) if so just click on OK
Now you should see the Change Icon Box opened. Click on BROWES... Pick the folder you have Icons in (I can’t help here I only know were mine are)
NOTE: it can’t be a .PNG it can only be an .ICO then Double click on the Icon you want, then click on OK then OK again.
Now you should back at your desktop RIGHT click on the Icon then click on PIN TO TASKBAR... Done.
Side note you really don’t need an ObjectDock Icon on your taskbar cause it runs in the system tray and you can set OD to load on start up…
Hope this helps!!!
P.S.
Oh and you may have to have ownership to do some of it... If so