It's a "stealth" ship because of two major things. Its hull's ability to deflect or absorb radar waves, and its heating/cooling exchange which was built in such a way that it can absorb heat into internal heat sinks for a limited amount of time, while cooling the exterior and engine emissions in order to reduce IR emissions.
With the stealth systems functional, you would have to find it by sight, which is hard to do.
They even discussed how the simplest way to disable many civilian craft was to disable their external emissive heat exchangers, since without them you couldn't run your engines for fear of cooking everyone inside. Warships had "tiger stripes" to limit the effect of losing one emissive surface would have on the ship's effectiveness. They also had methods of dumping massive loads of heat by ejecting molten salt (with an magic^w magnetic field collecting the cooled salt near the tail of the craft).
Such stealth ships couldn't maneuver much, but they could only be countered by other stealth platforms in a cat and mouse game reminiscent of Cold War submarine contests.
Maybe the "stealth" weapons of space combat look a lot like blimps.
They use big, cold, dark tanks of compressed gas for thrust. No combustion; just spraying compressed gas for propulsion/steering until they're close enough to the enemy target.
Then and only then, they activate active engines (or fire missiles with active engines) for the attack.
I'm not sure if those physics remotely work. I guess you could at least get up to a few thousand km/hour with a decently big enough tank of compressed gas in space, when you don't have friction or drag to worry about.
Dark on the visible light spectrum, sure. But if you have active engines or live crew (or both), you will be much warmer than space-at-large. Asteroids are tricky because they're dark AND cold.