Black Melanoids range in color from grey to brown to dark black. They have an increased amount of melanophores (dark pigment). Sometimes they can take on a silver or even lavender colored tone. They produce no shine (iridophores) Most melanoids have a paler grey or purple belly. Sometimes they can look like a dark wild-type. However, they lack the shiny ring surrounding the pupil that a wild axolotl has.
The juveniles often change color based on the color of substrate. They will try their best to blend in with it turning lighter when housed on a light color and darker when kept on a darker color. This is SO cool to watch. They tend to darken as they age. However, there is no steadfast rule on when that happens.
One thing to note-- the term "Melanoid" is often confused with meaning a "Black Melanoid". This is NOT the case! In fact, there can be leucistic melanoids, white albino melanoids, golden albino melanoids, and copper melanoids. "Melanoid" itself means the animal has more dark pigmentation and no irridophores. In turn, this only means the specimen is a black melanoid if it does not also carry two albino and/or two leucistics genes.