The battle cat's site (linked at the end of this post) has a veritable treasure trove of information on bitmap and colour table editing by Hamish "HAS" Sanderson. And I'll advise you to read it all if you ever hope to release your scenario.
For the meantime though, you seem to be doing a few things wrong and overlooking others.
1 - Why are you using "Import collection from PICT" to add a single bitmap? I wouldn't use import collection from PICT to begin with, it's very buggy. Simply choose "Add new bitmap" from the same menu, then cut and paste from a photoshop image indexed with the colour table in the current collection.
2 - Actually, you really do need to read HAS's colour table guide. You need to understand the how & why, do's & don'ts of colour tables, starting at the basics, before you actually start playing with them.
3 - The other point I was going to make was that you don't need to worry entirely about bitmaps looking funny under one colour table. Remember you can define what colour table a particular monster is going to use with your physics model, so having some bitmaps looking weird under another is not a problem, as long as said monster doesn't use those particular bitmaps. There's several monsters in Apotheosis under one collection, with clashing colour tables. But you'd never know that when you play the game.
(Hahahah...WHEN, I'm so slack).
//t
