Neither colours nor aesthetic judgments are arbitrary since the latter are based on sexual preferences and on disgust reactions which are biologically ingrained.

Determinism would entail that there are no accidents, that every event is naturally necessary. But scientific theories are really models that simplify phenomena, so many so-called natural laws posit probabilities, as you say, not necessities.

Moreover, physical events are more necessary than the higher-level complexities that arise for the special sciences, so the unmodelled interactions between complex systems is bound to generate at least apparent accidents.

Finally, this is just a semantic question about what we mean by "accident." By saying that life's emergence was accidental, I meant it was unintended and that it came about by the same enchanted, zombie-like, mindless order inherent in every other godless natural phenomenon.