You can only use custom colors for the Display Bottom Classification using the Variable color Track. It appears that the colors are otherwise fixed. Changing the gain of the sounder can also have some effects of the color/classification.
(Info found by searching "bottom discrimination" in the online users guide)
I have tryed differnt gain settings without results, thought it would work also.Fish in
generally shallow water 30 to 130 ft alll I can display is green and yellow colors sand /gravel thanks waterlogged