Before I settled on different operating schemes, I found myself planning on doing a couple of C&O engine projects, so it was an easy choice to base one of the operating schemes on C&O.  This allows me to add different color scheme variation to the whole "fleet".
 
Due to the creation of the Chessie system in the early '70s, paint schemes are quite different between the two operational eras.  For the mid-60's era, there are GP9s #5924 and #5927 in the C&O blue scheme.  For the mid-80's era, there is GP15T #1504, GP30 #3022, GP30 #3030, all painted up in Chessie colors.
 
I also plan on decorating a GP30 in the as-delivered B&O dark blue sunburst scheme, and a GP35 in B&O dark blue.  But I won't get to those for awhile.