different wall colors for new and existing construction

[joeybuilder]

see other thread of same title

[David J. Potter]

Far as I can tell, selecting one, say, interior partition and changing its color results in same color being applied to all interior walls.

You have observed the default behavior correctly. Part of learning the software is finding out for yourself what it does and does not do (is not programmed to work as we might it like to be, it is as and how it is).

I do a lot of remodeling plans professionally, what I do is to make an "as built" of the existing house or area of the house (that depends upon the scope of desired work).
Then Make a "save as" copy of that as-built plan to make or start creating the desired changes. You then have the as-built to compare and show so people can clearly see what changes. The as-built plan usually then becomes the demo plan where I add notes and other 2D CAD to indicate, in plan view what walls are to be demo'ed and torn out.

That method works for me and I recommend it to you. If you have Home Designer Pro, look under the "Build" drop-down menu under "Wall-Hatch Wall" and look up "Hatch Wall" in the "Help files and or Reference Manual" and study how to properly use the tool, then practice using it in a SIMPLE TEST PLAN till you are certain how it does and does not work, then apply it to your as-built plan to halo your demo walls that are to come out.

DJP