Hi Burr, actually colors are being written to IGES format currently.

For example I made this setup in MoI and then exported to an IGES file:



That IGES file then loaded into Rhino looks like this:



Loaded into ViaCAD looks like this:



Loaded into CoCreate looks like this:



Which program are you trying to import the IGES file into? Are you sure that it supports reading in colors?

I'm not quite sure about STEP, I'll take a look at that.

- Michael