By definition an ideal black body ⚫️ is a complete absorber that is no radiation in any spectrum goes reflected by it , which suggested that it should appear dark or black
On the other hand by consequences of its complete absorber property its also an complete emitter, i.e it should have come color .
Both contradict. So what's the correct explanation. And should a ideal black body always appear visually black or dark
When you look at an object what you see is the light coming towards your eyes from that object, and that light can be due to light reflected from the object or light emitted by the object (or both). If I look at you the light reaching my eyes is light reflected from you. On the other hand if I look at the Sun the light reaching my eyes is light emitted by the Sun.
So there is no contradiction in a black body not appearing to be black. It just means we are seeing the light emitted by it not the light reflected from it. For an object to be black it would have to both reflect no light and emit no light.
Black body radiation is a mathematical fit to most , note* not all, data gathered from the reflection and absorption of radiation from material bodies . This is the radiation wavelength related to the temperature, the one emitted by the body under observation.
Note the wavelengths of visible light emitted from the object and the corresponding temperature of the body in the curves. Room temperature in Kelvin is 293K. So the black body radiation emitted by objects around us is not in the visible range. They will appear black or colored to the eye, according to the reflections and the incident light .
You ask:
And should a ideal black body always appear visually black or dark
It will depend on the temperature of the body, if high enough it will emit light, for example iron heated to 1000K.
*The black body curve is used for fluids and gases too, but it is an approximation, example . It is an approximation for the sun spectrum too.
