Hi Saul, The simplest method is to use the Chimera command "rainbow chain". It gives each chain a different color progressing from red to blue. Use menu entry Favorites / Command to display the Chimera command line at the bottom of the main Chimera window, then type in "rainbow chain". If you want other color schemes you would select each chain and then color it. For example you could use menu entry Select / Chain / A, then menu entry Actions / Color / Orange. Another convenient way to select the chain you want is to click with ctrl-left-mouse button on a single atom in the chain to select that atom. Then press the up-arrow key on your keyboard once to select the containing residue, then a second time to get the containing chain. Then use the Actions / Color menu. One last hint. It can be painful to keep going to the Actions / Color menu. You can "tear-off" this menu to make it a separate window using menu entry Actions / Color / - - - - -. The "- - - - -" is the topmost menu entry. Tom