darto: clearly very clever but far too obscure to even get started and more than one solution which made it even more impossible (2 years, 11 months ago)
Primrose: The downside of trying for many crossovers is the loss of uniqueness. Also I find your categories too obscure. Nice idea, though, all colours. (2 years, 11 months ago)
mark: Really well put together, guessed all connections but could only get 1 because they all fit into each others groups (2 years, 11 months ago)
Not unique: The 4 grids are supposed to solve to a unique set of solutions. If 1 clue from a group can be swapped with another in a different group, without changing the solution of either group, then it is not unique.
The more red herrings the better, but I can see at least 4 solutions, using the 16 clues given, that fit your solutions.
Please bear this in mind. (2 years, 11 months ago)