Task Managers:
Red
32-bit 
64-bit
Yellow
32-bit
64-bit
Blue:
32-bit
64-bit
Purple:
32-bit
64-bit
White:
32-bit
64-bit
How to use:
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Download and run Task Manager Replacer.
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Download any of the Task Managers given above and drag and drop it into the program.
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That's it. Now whenever you open Task Manager, you will see the new color which you chose instead of the default green color.
If you ever wish to revert it again to the default green color then run Task Manager Replacer and click Restore.