Maybe it's because I got used to the sound signature, but honestly I think they are fairly neutral.
Of course you can have more neutral cans, but don;t forget that one man's 'neutral' is another man's 'bright'. I think that what you consider neutral is something I consider bright.
I think the only way to measure if a headphone is neutral is to have a perfect recording of an instrument, or musical piece played through the headphone in question. The compare this side by side with a minimal delay to the real thing.
Seems pretty hard to do well in practice, don't you think?