Are you talking about the 'filter' setting, or the 'wash' (i've forgotten what it's called) setting, part of the 'monochrome' Picture Style?
I don't have a 650D, and i shoot RAW on my 7D and post-process in DPP, so this may not be what you're asking:
The RAW file captures all colour information. When you process the RAW file as a 'monochrome' Picture Style, you can choose from Red/Yellow/Orange/Green/Blue 'filter effects'. This pocesses the file to exactly the same as using old-style coloured filters in front of your lens (like a yellow/orange filter will make a blue sky darker in B+W).
Then there's the 'wash' setting, which takes the monochrome photo, and changes the White to whatever you select. So instead of Black+White, you get Black+Red, Black+Yellow, Black+Blue, or Sepia.
The filter setting is very useful for me, I take a photo in RAW, then when I get home I can process it to whatever filter makes it look the best. Using B+W film I have to carry a bag of different-colour filters, try each out in front of the lens to see what it looks like, then try to imagine how that would look in B+W through a viewfinder.
The 'wash' setting is kind of pointless, unless you want to do some of those Andy Warhol ripoffs...