Reverse colorbar

Hi I was wondering if you could help me out with which command is needed to reverse the colorbar scale I am using the Jet colorbar.

Use the -Ic option in the colorbar module

Is this for GMT 6? it is not working …

-Ic is an option in makecpt and grd2cpt, not colorbar. So if you want to reverse a scale you will use makecpt to reverse the scale first.

Do you want to reverse the color of the cpt (this will modify the colors of the map) or to reverse how the color bar shown (this will NOT modify the map)?

I want to revers de colors of the map so they can be consisten with other maps scales as well the diference is tha the depth is this Map are in positive and in the other map teh convencion changed and are in negative values. thenI did what was suggested by Paul used the grd2cpt

gmt grd2cpt -R-073/-060/06.5/013.0 -Cjet -Z > colors_1.cpt -E -Iz

now the colors are right , the colorbar is right as well in the values but but I would like it to begin in the min value and end in the max value and read the color bar with the 50 km to the left and the min value to the right.

I hope I could explain myself

colorbar documentation says
Give a negative length to reverse the scale bar