U can change the light order when building a model. The NUTCRACKER previews will work as expected, the physical lights will have accurate colors. The PREVIEW will not show colors correctly. For the preview tab to show correctly model start channels need to start on a channel that after u divide it by three you have a fractional .3333333.
Example start channels of 1,4,7,10 are good. 2,3,9 are not.
I consider this a bug in PREVIEW. As we completely rewrite the UI for xlights 4, we will not be revisiting the PREVIEW screen until January.
Again, u can use color order in models it will make correct colors in NUTCRACKER tab and the physical lights will be correct.