I was told that exposed developed colour film can be used to block visible light for infra-red photography. Where can I get some of this, or can I do it myself? I have a roll of 400 ASP colour film that I've exposed, but don't know how, or if, I can develop it.
I don't know about colour negative film but unexposed slide film works once developed. Slide film needs to be transparent to IR by necessity, otherwise it could be damaged by the heat from a projector bulb.
There's no guarantee your film will work and unless you can develop colour film yourself, a cheap IR filter from an auction site may work out cheaper (and work better) than paying for your film to be processed. I've got 720nm and 950nm IR filters for use with my modified Olympus C5060, both are Chinese no-brand filters that cost very little and they both work very well.
Incidentally, you don't want to invest in expensive filters until you know the IR characteristics of your lens. Some lenses (on both fixed lens and dSLR/system cameras) show a "hotspot", an area in the centre that is lighter and has reduced contrast. My Oly C5060 doesn't have this issue but my old Minolta Dimage7 definitely does. This issue can affect both digital and film alike as it's down the lens design and not the imaging technology.
I'm not familiar with using developed color film for IR; however, I have used a project where the inside of a 3.5" floppy disk was used. It should be noted that was used with a webcam and not a "proper" camera.
If you want to develop a cheapo way is with coffee and orange juice, but it takes away the color so it probably won't work for your project.
Judging from the way you spelled color, you might want to check with anywhere that sells Ilford or Agfa. They should have or be able to order a proper C-41 kit (mine was made by Jobo). If you were in the States I'd suggest Amazon or B&H.
Hopefully that can get you started.