Dark earth is rich in organic matter hence the blackish colour. Russians call it "chernozem" where "chern(y)" means black and "zemija" earth. If you want to portray harsh conditions of eastern front this colour will do the trick. Remember: actual chernozem is close to black only when wet, when dry it shows numerous shades of grey and brown! This  4 colour premix acts just as the real thing.  Brownish when dusted deep dark grey with a hint of brown when wet! CLICK TO SEE FULL PRESENTATION