In his Old Ireland in Colour project at the Insight SFI Research Centre at NUI Galway, Professor John Breslin uses DeOldify, an open source tool, to bring colour to archive images. This photograph from the RTE Archives shows women protesting outside Mountjoy Prison, Dublin in 1920 - note a photographer with a camera to the left of shot.

So how did Breslin choose what colours to use? "For this photo, we used three variants of DeOldify to achieve variability in the coats and clothes of the marching women, using commercial implementations (on and," he says. "This gave us a variety of colours including green, brown, gray and navy coats that we then trimmed/manually adjusted in Photoshop." 

Breslin also made sure he looked at the image with fresh eyes. "As there are a lot of faces, we went through the image a few times to make sure that none had been missed out on (e.g. the partial face of the boy behind the man on the front left). A friend of mine who also colourises, Matt Loughrey, said that it's a good idea to put the image away for a while and come back and look at it with fresh eyes. It worked here as I spotted some faces I hadn't fully colourised!"

Adding colour to images requires close attention "Most women (but not all) seem to be wearing gloves so we assume it was the style or a cold day," says Breslin. "There appear to be some trams in the background but they are too far away to add any colour. We added some very, very light blue sky in the top corner where previously there was some shadow on the original. We adjusted the colours on the signs slightly (red and green). Various marks and scratches were removed manually in Photoshop, and other details enhanced. The signs in the background seem to say "Join With Our Protest" or some variant."