Eli5: How do photo restoration artists know the supposed colors of greyscale images?

Question

Are the colors based purely on their assumptions/imagination, or do the greyscale images retain some sort of data that tells what color on what part?

In: 641

Answer 1

I would think that some one that is color blind would have it easier. All their life they have been told this is red, this is yellow, this is green. So they see different shades or grey from white to black. If only blind to certain colors (read and purple specturms look brown) that could make it hard.