convert colours from gif to gif without lose the transparency

Hi list,

I'm new using ImageMagik,Im trying a very simple thing:

I have a gif image with transparent background an I need to change the gamma
of colours to a new one gamma of colours from a file (can be from another
colour definition way?) living the transparent are equal.
With this command I can change the colour, but Im loosing the transparent
area!:


$ convert originalColourAndTrans.gif imageWitTargetColours.gif -clut
output.gif


What Im doing wrong? maybe its not possible?

Thanks in advance!
Oscar