I'm jealous of the first situation. I deliberately make CAS "parents" with recessive traits like light blue eyes and red hair, then "breed" them in BodyShop to create the Sim I'm actually going to play to give recessive variety to their kids. As far as I know, brown and dark blue eyes are both dominant to light blue (and custom is dominant to everything else), and Sims created in CAS are homozygous (have 2 identical copies of the expressed gene) unless you use my trick.
Do you have, accidentally or on purpose, the hack that makes all Maxis eyes equally dominant? You still shouldn't have got eyes that don't match either parent, but it would be a partial explanation.
Another silly question: are your light blue eyes custom (rather than default) and not geneticized?
Rather than going through all the trouble of actually having babies, you can try different combos in CAS using the pacifier. It's slightly different from the game, especially in face mixing, but it should give you some idea what's going on with the eyes!
I don't have any mods for equal dominance in eyes, and all I have is Maxis genetics. The mother was a redhead with dark blue eyes and the father was black-haired with brown eyes. She was s1 and he was s2 and they had a daughter with s1, red hair and light blue eyes. The second couple, the mother was blond, s1 with light blue eyes and the father was s1 with dark blue eyes and blond hair. Their son was s1, blond and brown eyed. The couples I used were all founders, so no previous generations incorporated that into the gene pool.
