Rise from the Grave doesn’t overwrite any previous colors or types. Rather, it adds another color and another subtype.

If the targeted creature is normally colorless, it will simply become black. It won’t be both black and colorless.

A later effect that changes the affected creature’s colors will overwrite that part of Rise from the Grave effect; the creature will be just the new color. The same is true about an effect that changes the affected creature’s types or subtypes.

A “creature card” is any card with the type Creature, even if it has other types such as Artifact, Enchantment, or Land. Older cards of type Summon are also Creature cards.