Hello there, I study water/ice systems and I have an algorithm which reads my trajectories and tell me if a certain water molecule can be considered "liquid", "hexagonal ice" or "cubic ice". So I can label each molecule at each frame as such. I am hoping to be able to use this data to create a movie where each group is coloured differently, and should a molecule change groups be re-coloured accordingly. I attempted this by running a PER-FRAME script which reads my labels from a data file, and colours the molecules. However I ran into a problem, running either of the following commands: colour blue,a :52 select :52 in the PER-FRAME script, or even just on the command line during an MD Movie does NOT work for me. This works for a single configuration file, but not during a movie. The command: color blue,a @OW however does work. I am currently using XTC trajectories, in case that is relevant. What might fix my problem? Or is there a better way I could be doing this? Cheers, Thomas