Jerry,
I hope your doctor is wrong in saying that you may not see certain shades of color. The reason why I tell this is because one of my classmates is color blind.We talked a lot about it. It looks like he can see all the colors in the test patch, including all the shades, but he can not combine the all the dots of different color together and make out the pattern. But if he takes time, look at each of the dots that comprise the number individually and analyze it, he can make out the numbers.
It looked like, altough he can see the individual colors, he had problems processing the entire image and recognizing it. It is like, you can read the indivicual letters in a word, but you can't read the entire word unless you read it letter by letter and put them together.
Another test that you can do is, look at color patches of slightly different tonality and find out if you can distinguish between them.
Now, it is very much possible that your doctor is correst. I am interested to know if the type of blindness you have is the same as my friend's.