My 1.1 juvenile (20" or so) N. nigricollis were pretty "hoody" and even fairly spitty when I got them late last year. However, now they've stopped hooding and rarely if ever spit. Being that they've gone from about 15" to just over 20", they're probably going to be the "dull indigos" that you describe. Oh well, I'm certainly not complaining, especially if mine have the genes to hit the 7 to 8' mark! I'd much rather work with a very placid huge cobra than a very aggro one.