it is a good idea to use colors for citations in hard bound thesis(printed copy) Do you think it is a good idea to use colors for citations in the hard bound thesis(printed copy)? 

I think it is a good idea to use colors to make citations more visible in the PDF files on the computer screen but not in the book.
I agree, don't use colors for citations or any other text in print.

Besides being potentially distracting or harder to read, it's often more expensive to print.