There are no pure black corns yet and even blizzards will often show some yellow residual pattern. The degree to which bloodreds turn red is also quite variable - seems the corn pattern is hard to eliminate. Bloodreds and blizzards are less frequent than other corn varieties in Canada, hence higher prices.
The black ratsnake starts out with saddles but becomes increasingly black with age, although many retain some of the saddle pattern. If you like the reddish look, everglades ratsnakes are relatively common and mature to have just faint traces of pattern with and orangy-red look.
For black snakes, the Mexican black kingsnake is one of the nicest - moderate size (4 ft), great gentle temperment, shiny jet black and great feeders. There are a few threads in recent past on this forum that have lots of pictures. They are a great pet species - and usually not too expensive.