Many people think that subjective problems have no solution. This isn’t true. All of them have provable solutions. It’s just that reaching those solutions is an impossible task for us at this time.
Which is better: red or blue? One of the main problems with this question is that it doesn’t say better at what. If the question was “Which is better as camouflage when in the ocean, red or blue?” One would obviously say blue. But since this isn’t specified, it essentially is the same as asking “Which is better overall: red or blue”.
No one knows what overall is. We have only a biased subset of the set of all possible situations of using red or blue. As humans, we can’t imagine how aliens might use red or blue. If seeing blue kills them instantly, to them it would seem as though blue is worse.
The phrase “car x is faster than car y” really means “car x is faster than car y in a large proportion of the set of all possible roads” (it’s almost always possible to design a scenario where the supposedly slower car is faster than the other).
To determine the answer to which is better red or blue, we need to look at all possible measures. Which is cheaper, which is bigger, which is faster, which is healthier and so on. We then add up all the differences in how red and blue are in these scenarios and whichever has the highest number is the best. It’s pretty simple. A way to improve this would be to use weighted voting. So maybe Not killing you instantly is more important than being brighter.
One might reject this and say “Assigning not killing you instantly as more important than being brighter is entirely arbitrary. No evidence you can provide will ever prove that one of these is more important than the other”. This is total nonsense. If you believe this then you must be terrible at making decisions – you are unable to evaluation potential futures as better or worse than each other. Your decision making would essentially be random. If you could evaluate the future, then you therefore agree that some universes are better than others by using some measure (it doesn’t matter what that measure is). Therefore some things are more important than others.
In summary, red is better than blue or blue is better than red or red is equal to blue. One of these statements must be true. Just because they can both be described as colours doesn’t mean that it’s impossible to separate them. Hitler an Gandhi were both people yet we can easily see which of those is better.