I tried directly using the ISM but it didn’t solve the issue. Also the row names are actually the same 0,1,2,… all the way to 64799 in both cases. It is just that in the first case I have one ISM that is instanced 64800 times but in the other case I have 180 of them that are all instanced 360 times each. The math is there just to transform the indexes going from 0-179 and 0-359 into one that goes from 0-64799. I made sure that this is the case by printing out the names in both cases and they do indeed match.
So the issue still persists and the coloring does not show up. Thank you anyway for looking into this!