One of the reasons filmmakers moved from blue to green screens is because digital cinema cameras record more color information in green. However, USB cameras process video differently, and we weren't totally sure what to expect going into these tests. Here are the results.
Note - to get started with the plugins and effects mentioned below, you'll want to watch these video tutorials.
We grabbed a frame from the 720P and 1080P camera with both a green and blue background. Then on Windows we ran the frames through WMM 6.0 with the Rehan ShaderTFX plugin applied, and on OS X we used iMovie with the Chroma-Key effect applied.
Also note that we lit our scene and chroma-key screen with daylight temperature LED bulbs. Fluorescent lighting can cause unwanted color shifting.
720P Camera Tests
In WMM green looks terrible. Don't plan to chroma-key in green with the 720p camera.
OS X is hardly better, even after tweaking the background extensively with the effect controls. The algorithm is confused, and thinks the blue stripes are actually green!
Blue in WMM is much better! There's a little fringing in the background, but it definitely works.
The same is true for blue in iMovie. Slight fringing in the background, but there's definite separation and the key looks pretty good!
1080P Camera Tests
Next, the 1080p Widescreen Video Webcam. Along with a higher-resolution image, the sensor in this camera more accurately reproduces color, so the results are cleaner.
Green still has issues in WMM. There's slight fuzziness in the background, but it's not as bad as with the 720P camera.
The green is processed much better in iMovie, with clear separation of the blue on the minifig's shirt from the green in the background.
Blue wins again. There's less fringing in WMM, and iMovie looks great!
When using the free chroma-key effects available in WMM and iMovie with the Stopmotion Explosion cameras, BLUE is better than GREEN!
Your camera may be different, and you may wish to run your own tests with both colors to see which works best.