Visual Search & Search By Color

I have 2 search questions:

I want to do a visual search - find similar images to a given image
I have ~55,000,000 many of them of people and new images are uploaded each day.
I have read some web resources. for example pinterest which I found interesting:

  1. Are there more interesting papers I should read about this topic?
  2. If I use some model let’s say: ResNet152. On how many of my images should I retrain it (transfer learning)… I assume the more is better.
  3. How should I do the nearest neighbor retrieval?

Another question about search by color.
For example google have it:

Is it also deep learning? How can it be trained without a color label?
Are there some papers about it?

Thanks in advance,

I think you’d get a lot of value out of the following link:

It talks about a lot of the issues you’re pondering.