from my extraordinarily limited knowledge, I believe Oscuro is simply a wrapper considered to be much darker than Maduro (more like a charred hot dog left in the coals).
Maduro = Dark
Oscuro = Black'ish
a side note, "double maduro" is generally classified as a cigar with both a maduro wrapper AND a maduro binder and thus has nothing to do with color.
I THINK I didnt mangle that too much.... someone who actually knows want to jump in?
