I don't know if they are required, but it is easy to figure out the codes. In PSE whenever you open the box to select a foreground color, it lists the # there. I actually just use this method to pick my pallette for the challenge. I open my photo and place it in a new document and then use the eye dropper to click on a color in the picture and then you have your color # right there.
I am sure others have lots of ways of doing it too, but that is what I have found easiest for me.