We call something subjective when there is no overall consensus on it. Or is it something that we have yet to be able to explain fully. Music; the theory of music is universal and objective yet tastes in various genres vary greatly. I don’t think we know why. Is the subjective someone we are yet to agree on?
Person A likes the colour Red but hates Blue. With Person B this is vice verse. Neither would be able to tell you why but a neurologist might. Something in the brain is making a choice and that must be to do with chemical/hormones/neurotransmitters making a specific pathway. This still doesn’t explain why that decision has been made. Could we then look at the possibility it is utterly random or is a deterministic approach required? Maybe it is genetic. A gene for liking the colour X that codes for a specific protein that causes hormone Y to, etc, etc. This is then deterministic for the time being. So how long has this gene been clinging on to each generation. Now this is just a regression back to a point just after the Big Bang when the fate of the Universe was decided.