Hi, This feels like a basic question but it has stumped me for a day now so here we go... I'm exploring ways of programmatically setting colours to find the most efficient method. This is for the 'custom coloured' case (residue-based colour schemes are not a problem). The simple version is to send as many 'color' commands as there are colours in my (Jalview) sequence: color #ffafaf #0:1.B|#0:5.B|#0:7-8.B|....;color #ffff00 #0:39.B|#0:44.B|#0:47.B|#0:77.B; This works, but doesn't seem to scale up well for large/many structures - I start to see Chimera using 100% CPU for minutes at a time. I'm trying instead to see whether setting a colour-value attribute is faster. I can set the attributes ok with commands like setattr r color green #0:1-84.B etc and confirm they are set with list residues spec #0:1-84.B attribute color but I can't figure out how to get Chimera to use the attribute value as the display colour. 'Render by Attribute' only seems to consider numeric (range-valued) attributes, not colour-valued. I thought perhaps 'my' colour was just hidden in the colour hierarchy, but removing other colours doesn't seem to help. What am I missing? Thanks, Mungo Carstairs Division of Computational Biology University of Dundee http://www.jalview.org The University of Dundee is a registered Scottish Charity, No: SC015096