How to find out the original colors in a black and white image if the exact color of individual objects is known?

Question

Image processing

Good afternoon. The task is to understand what color one object in the photo has (not the exact code, but at least it is blue, red or green). The image was converted to black and white by the author in order to hide this color. But there are objects with known colors in the photo.
According to my logic, if the image was converted to black and white in the editor, you were just subtracting rgb colors. Maybe it's possible to restore the original rgb mask focusing on individual objects in the image?

Answer 1

Converting from RGB to Grayscale is an irreversible function. For example, in the television standard CCIR-601 it is set as Y = 0.299R + 0.587G + 0.114B, and in sRGB as Y = 0.2126R + 0.7152G + 0.0722B.

Answer 2

There have been attempts to solve this problem using machine learning and neural networks. More or less successful. We trained the object recognition grid in the picture, then taught which colors dominate in the image of certain objects, then a couple more know-hows, including "shamanism" with a brightness channel, etc. The result is not brilliant, but quite plausible. You can’t restore an artistic picture, but a simple documentary photograph is close enough to the original.
Only this task is definitely not for people who have not dealt with this topic (image processing using machine learning methods) before. And certainly, the logic that you cited in the question is not involved there.