When marking more animals in the "Show Identified Animals" view, keep the identified animals blue after the first selection

[vladimirg]

Steps to reproduce:

1. Mark a few animals.
2. Navigate to a different frame.
3. Press "Show Identified Animals" - the identified animals will be marked in blue.
4. Press "Mark Worms" and mark a non-detected animal.
   Expected: the marked worm will be green, and the blue worms (which were previously identified by the algorithm) will keep being blue.
   Actual: the blue markings from the previously-identified worms disappear, making it difficult to continue marking just those worms that the algorithm missed.