what color should I post next for trade?

[UltimateArtifacter]

I've posted all my blacks, now which should I post?

[Gorzo]

Blue. The most used color in tournament play, so I would wager blue cards see a bit more trade than other colors also.

Or lands. Every deck has 'em, every deck needs 'em and they trade well. Probably a quarter of all the trades I've done, lands were involved.