Why when I use green for foreground color and go to Fill and use the option of Foreground color the selection is filled with black? Also why when I open a file with a green square, it also turns to black? And since I am asking questions, how do I get back the ability to get content and search help within photoshop, instead of always being directed to Adobe online? I am using CS5. Many thanks, Jim.
Nobody can know. Your description is too vague to make any sense of it. You get be operating on an isolated channel, you could have hardware issues with OpenGL acceleration, you could have applied some layer style that overrides your fill. Too many potential things, so provide screenshots and more info. The help can be opened by setting the relevant option in the community help client to prefer local content.
If you have an AMD graphics card then the problem may be the driver (pixel with red component of 0 being displayed as black), and a fix is in Catalyst 13.4 which you can get directly from AMD site.
Check what mode your editing in and what your filling. Layer Mask like channels and grayscale mode only support nutrals Black, White, Gray, no colors dark green would look black.