How to design a translucent watermark

I am Henry,I would like to know how I can create a watermark of a coloured logo,it should only be visible when the paper is tilted.I don't know how to call that design but it is washout-like and only clearly visible when the paper is tilted.It is used for authenticating the document,kindly help,I can rephrase the question to significant granularity if not understandable.thanks
