I use the colorization neural filter a lot but there are simple improvements that could be made. Two come to mind immidiately...
1. The focal point image is far to small to apply accurate color targets to the image
2. When adding color focal points there should be a menu of colors to choose from that produce the same colors the colorization neural filter creates. For instance, Flesh, foilage, water and sky. This would allow a person to help the A.I. out and identify things that it didn't find correctly.
Sorry if I'm just missing something and these features are already there.