The easiest method is to use a chroma keying approach. If the writing is green, for instance, make sure that nothing else green shows up in the shot, then use a saturation adjustment inverse-keyed to green (so it effects everything in the shot that isn't green) to turn everything but the writing black-and-white. How exactly you do this will vary depending on what software you're using.

Another, more work-intensive approach that might be to use travel mattes combined with chroma keying to isolate the colored element. This may or may not produce better results, depending on your footage.

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Andrew Gingerich
Exploding Goldfish Films
Check out my blog at http://www.exgfilms.com
and my reel at http://portfolio.exgfilms.com

Thank you Andrew I found your advice most helpful, I used elements of your advice and added to it.

In the end I shot some practice footage against a green screen, then I used a Chroma key with in Final cut. Once I perfected the green screen image I sent it to colour where I desaturated the footage and then tweaked in the colour I wanted the text on the tops to be.

Originally I had thought about duplicating and layer masking the footage with an 8 point garbage matte, but that would of meant key framing the edited footage once i had cut the rough edit together how he wanted it. Which is considerably more labour intensive than the method i actually used instead.

Thanks for your help, it really means a lot to me. Cleary.

www.myspace.com/b31_film_productions

Glad it worked out for you. Color is an incredibly powerful piece of software.