Information from the Chessbase website:
The Colle System is rather a playing scheme than an opening. White plays d4, Nf3, e3, Bd3, 0-0, Nbd2 and possibly c3 - nearly regardless of what Black replies. Opening knowledge is of secondary importance. Exactly this is where the author starts his work, prioritizing on explaining plans, patterns and typical mistakes. For example, two chapters are titled "Ten inspirational games" and "Eight warning games". However, Oleinikov naturally also deals with opening theory in the classical sense and discusses the critical variations, at one point showing himself surprised: "To my amazement, none of my opponents has reached this crucial position so far". Certainly a hint that the second players know too little about the Colle System and rather play it by ear.