Fun challenge!  I always learn so much from these things.  The tutorials are a bit over my head, but I did figure out a coule of different ways to make this happen.  Thanks!

@ Tom:  I'd love to see your pepper/tomato image done a slightly different way.  Maybe if you took the original image with the original colors and desaturated everything but the knife blade?  The only color then would be the reflection of the veggies in the knife.  Just a thought - it might be kind of cool.  (It might not, too - sometimes things look better in my head than they do on the screen!)  I wouldn't "dull down" the colors that were left, I don't think.

"If your pictures aren't good enough, you're not close enough."  ...  Robert Capa