The phrase ‘(In) black and white' implies for something (like deal/agreement etc.) written on paper in ink. One can always back out of a verbal agreement, but in case of a written agreement, it is not possible.
1. I have given my statement in black and white.
2. I have no faith upon you; I must have the statement of yours in black and white.
3. Don't worry! Everything is in black and white so there is no chance of fraud or cheating.