SelDup choose the duplicates in one group?

I have two groups of curves, one old, one new. I want to select the duplicate lines from the old and delete them. When I run SelDup, it seemingly randomly chooses which group to select the duplicate from. Is it possible to force rhino to always choose from one set which duplicates to select?

See attached images: 1 group black, 1 group red curves. SelDup, moved to the side, chooses half the lines from black, half the lines from red.

Thanks

You can do a SelDupAll, temporarily lock the rest of the objects, then select by color or layer or…