Fixed colors for grade

[cicdguy]

NEST/osprey/pull/31#issuecomment-14703)

Also another good-to-have, but could-be-added-later thought. Based on some of my recent requests, since we usually use grade as block_color if not NULL, whether we could set that if the block_color is grade (or if bar_color in counts_r, counts_l is 1-5?), the default to be

scale_fill_manual(
        name = "Grade",
        values = c(1 = "darkgreen", 2 = "blue", 3 = "orange", 4 = "red", 5 = "black")
      )

Provenance:

Creator: gogonzo