As has been said, the Metaethics Sequence attempts to articulate a position on this.

My summary, take it for what it's worth:

Some things have more value than other things.
Talking about whether that value is "inherent" tends to cause confusion, but there is some calculation that can be performed on measurements of a thing to determine its value.
That computation is complex and has many inputs and is effectively impossible for humans to articulate or even understand completely or precisely; it's not anything as simple as "human life" or "sentient life" or "happiness" or anything like that.
That computation will reliably return the judgment that a human being is more valuable than an equivalent mass of paper clips.

Words like "right", "moral", and so forth are best understood as references to that (as-yet-unspecified) computation, just like the symbol "+" is best understood as a reference to the operation of addition.
If someone misunderstands what "+" means -- for example, if they understand it to be a reference to multiplication instead -- they might agree that "2+2=4" but assert that "3+3=9". That's not because they disagree about addition, it's because they disagree about what "+" means, and they are simply mistaken about what "+" means.
Similarly, if someone misunderstands what "right" means -- for example, if they understand it to be a reference to the speaker's values, rather than a reference to that specific computation we talked about a second ago -- they will make false statements about what's right and wrong. That's not because they disagree about right and wrong, it's because they disagree about what "right" and "wrong" mean, and they are mistaken.

I should perhaps note that I don't hold this position myself, and may be mischaracterizing it.