(sorry I can't remember how).
What you do is choose colours on the side-I chose blue & purple, below.
The software scans all the millions of images from flickr, or Alamy and
processes them according to colour.
In the one below, I have used red & yellow:
You can choose up to 10 colours.It's limitless & quite fun for composing a mosaic of digital photos.
Click here to have a go.