1. Yes, rabbis who answer questions regarding stains and discharges on bedikot must do extensive training. There are community rabbis whose training is not as extensive, and they often consult with their own rabbis when they are unsure. More than anything, practice and practical experience in this field is what gives them the tools to asses the different colors. Certainly in the training programs to become the rabbi of a community a lot of emphasis should be put on this area of halacha.
2. As mentioned in our previous answer, the problem with bedikot is that there is much debate about the halachic status of certain colors, and there are different traditions concerning those colors. It would be presumptuous to codify in a book one specific tradition regarding these colors, as this would ignore and disregard the other traditions. This would be similar to teaching a halacha according to Sephardi ruling, while disregarding that there is a parallel but different Ashkenazi ruling. Another reason is the complex nature of ruling regarding colors, which requires practical experience. Training usually involves working with a single rabbi and becoming familiar with his tradition regarding different colors. Factors other than the color itself are also taken into account. Another problem with printing a color chart would be that the colors could change in printing itself or fade over time.
3. The information about different situations in which a stain is found are pretty straightforward, though there are differences of opinion and different rulings as in most areas of halacha. The colors are a bigger problem, as traditions in this regard are transmitted orally and dependant on the judgment made by eyesight of different rabbis. Ruling in halacha is not an exact science, as the Torah was given to be kept by human beings, and its rulings intended to be determined by our human capabilities. That said, Judaism takes tradition very seriously. We are unable to trace back the sources of all traditions and determine which is correct, due to the unfortunate dispersion of the Jewish people over the years. It is also unclear that we are meant to find the "correct" tradition, rather than respect the fact that the Torah can be interpreted in different ways. It is important to find a rabbi to whom one may consistently ask questions, but that rabbi should be one that the couple (or individual) relate to and can speak with frankly.
We commend your sincere search for answers to these important questions. Many women who observe the laws of niddah deal with the same issues, and we will be happy for you to continue using this resource to ask. We were sorry to hear that you are unable to find an address to speak with directly. If you would like to tell us where you live, perhaps we can try to get you in touch with someone who is sensitive to the issues you have raised, at least by phone if not in person.
We wish you much hatzlacha in your continued search of your Jewish world.