there different then a vlamingi .there both a naso just one is a naso vlamingi and the other is a naso lopezi.and it sounds like you should be fine TeresaQ a 150 is fine for one.just remember they eat a lot.
lighting can a little.i have seen niger's come in different shades.just feed him/her a varied of food and good clean water and it should be nice and colorful.
it should be fine.i have a stripped dogface and he can change color from dark to light.it's all about there mood or how he/she is feeling.or it can be a sine of a sickness but as long as he/she is eating good and acts normal you should be fine.