one view from another so you could try to predict the color image from the grayscale putting the grayscale from the color doesn't actually need any deep neural net all you need to do is average two pixels and quantize and you're going to get something that is reasonably grayscale and in exactly the conversion is done it's a weighted average of your RGB pixels so but the other version which is predicting the color from the grayscale means that you have to add some new information to what's already there because you don't have any information