Unfortunately for The Colbys, it was cancelled just at it was hitting its stride (going up against Cheers will not help any show’s rating). Based on Dynasty, we get some resolution to the Colbys Season 2 Cliffhangers:
Frankie survives the crash and runs off with Jason
Monica has no contact with Cash or Scott so they must have gone back to Washington D.C. and Monica decided not to fight
Miles likely did not find Channing since he was with Fallon in the Reunion
The aliens return Fallon and her talking about it ruins her marriage to Jeff
The real love triangle
Of course, if there was an actual Season 3 of The Colbys, things would have been different and we can only speculate. So, let me speculate:
Frankie was going to be killed off. I believe Katharine Ross said she was not coming back and getting rid of Frankie sets up some great storylines: Jeff blaming Jason for Frankie’s death and a love triangle among Jason/Sable/Zach (which should have always been the primary love triangle).
There should be the custody batter for Scott.
Miles finds Channing and stops her from getting the abortion. The plot line with Lucas (Jason’s lawsuit) had not been resolved. And, Channing has a younger brother who could make an appearance.
Bliss and Kolya are definitely gone.
Even though Phillip escaped from the crash, you can spend a few episodes pretending to look for him and then just ignore him. (As was done with Dr. Nick Toscani and Joel Abrigore). Maybe a Phillip can appear in a Season 6 of The Colbys.
As for Fallon and the UFO - it should be used the same way that it was used on Dynasty - to drive a wedge between her and Jeff (intensified by Jeff fighting with Jason).
Obviously, there would be newer characters and storylines but that is how I would like to have seen the cliffhangers of Season 2 resolved. (I really, really wanted Frankie to die!)