What is the fastest way to do this?

I have captured the screen image and put in a picture box set to the size of the screen. I have another picture box that also has a screen image in it. What is the fastest way to compare the 2 pictures against each other pixel for pixel checking for color changes? Also, how would I save that color off? Any code exaples would be great.

Use the BitBlt function. Look up a tutorial on AllApi.net, and use vbSrcAnd as the raster operation to "blit" one image on the other. Look at the example for what I mean.