Question

What will a paper appearing black in sunlight appear in red light?

Answer 1

Black ( with little bit red complexion)
An object is black because it absorbs most of the visible light fall on it leaving very less light to go your eye and just confirming the presence of object.
So if a piece of paper is black in sunlight then it is absorbing all the visible light from sun. So it doesn't matter if you see the paper in red light as it will still absorb the most of the light fall on it reflecting back very little light making the colour black with little bit red complexion.