The hext value has 3 digits. The hex can be translated into a base 10 number from 0 to 255. That number is the color value for that number. That combination gives white. If you just want to click on a color and have the computer tell you what the hex is try the ColorServe Pro server.
Forms are a good way to get information from a user.
There is good tutorial written by Carlos A. Pero that does a good job of explaining forms. To make transparent gifs you need to use a special tool. I use giftrans. This copy is compiled for linux. Just run it without arguments to get help.