Hello Prafful, You should look at the ChimeraX help, not ask some AI that will often make up wrong answers (at least currently). As it says in the ChimeraX help, <https://rbvi.ucsf.edu/chimerax/docs/user/commands/color.html#simple> ... "color fromcartoon" colors molecular surfaces to match the cartoons of the corresponding residues. It does not color other things, only molecular surfaces, and secondly, "corresponding" means the surface in the same model as the cartoons, not some other model. As also explained in the help, <https://rbvi.ucsf.edu/chimerax/docs/user/commands/color.html#target> ... the "target" option is only to specify whether to color atoms, ribbons, surface, etc., for example "target a" means atoms - it does not specify a model number. If you want to copy the coloring of some model to a different model, take a look at the "mcopy" command instead: <https://rbvi.ucsf.edu/chimerax/docs/user/commands/mcopy.html> I don't know what exact command will work in your case (it depends on the details of your models) so you will have to look at the help link above for additional options, but maybe something like the following. mcopy #1 to #2 settings c I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. UCSF Chimera(X) team Resource for Biocomputing, Visualization, and Informatics Department of Pharmaceutical Chemistry University of California, San Francisco

On Jul 11, 2025, at 5:19 AM, Prafful Sharma via ChimeraX-users <chimerax-users@cgl.ucsf.edu> wrote:

• Dear ChimeraX Developer, I was recently trying to color a model in chimeraX based on a similar model with the same chain IDs and residues, and so I was using the command color fromcartoon #1 target #2 as specified in the documentation however I am receiving an error that says " Expected a color or one of 'byatom', 'bychain', 'byelement', 'byhetero', 'byidentity', 'bymodel', 'bynucleotide', 'bypolymer', 'fromatoms', 'fromcartoons', 'fromribbons', or 'random' or a keyword". I assume it is asking me to add a specific color name/code, but the other models have many different colors. I tried multiple turnarounds and even took help from different AI models, but still could not solve the error. I therefore think the functionality is not active, or there is some issue with I am not able to figure out. Can you please let me know if this functionality is working, or if there is any other way I can do this? Thank you for ChimeraX and your kind help! Prafful Sharma