I've been thinking about it
The Java libraries have all sorts of image processing code, so it wouldn't be all that hard to create an applet to do simple RGB combinations. The tougher challenge is getting the color right. For a long time now I've had this idea about using the formula to convert wavelength to RGB to create color images from arbitrary filter sets. Doing something about it has been a matter of finding time...unsuccessfully so far.
Chris provided a useful link in his reply to you. I happened upon a Java applet for doing anaglyphs, which seems like a natural feature to add. Stay tuned for version 2.1.