Colourise old B&W Images
Black and White photographs and illustrations are ideal for colourising projects. Flickr Commons has thousands of suitable images and is an excellent place to start. The example below was made using free online browser based photo-editing software to recreate a ‘traditional’ hand coloured look. 
Possible Learning Activities & Outcomes
  • historical research
  • recreate the feel of a traditional media process using digital tools
  • develop image editing skills
  • develop photo-editing skill
  • digital storytelling
  • critical analysis of images
  • visual literacy

Comparing hand coloured images with their B&W originals, such as the examples above created by  Kelly Short. This activity might suggest questions such as; "does colour change how we react to the picture?”

Colouring using AI (artificial intelligence)
There are a number of online tools that automatically colour B&W images using AI/machine learning. These tools are trained using millions of images in image databases. Some subjects are much better suited than others to take advantage of these processes. Images with a human presence or landscapes work better than pictures of objects. Most allow you to upload your own images for colourisation. It is important to remember these are ‘machine guesses’ and may not correspond to the actual reality when the B& W images was shot. 

Online Tools
Deep AI

Photo-editing Apps/Software
Sophisticated tools such Photoshop (expensive) or Gimp (free and open source) both have a steep learning curve. However there are a number of free online photo-editing apps and tools that you can use to get started with and experiment in colourising - some are listed below. I have not included Flash based tools. It is also worth checking out some online tutorials, especially from professional colourists who share how they achieve their results. 

Photopea  An advanced online editor, that can be used by professionals and students. Includes layers, blending modes masking  and mulitple important and export formats. 
Pixlr AI based online editing - advanced and basic options.
Colorize Photo Specifically designed to paint over a B&W picture using a colour palette from a reference image, (you can upload your own).

Further study
Some of the finest work in this field has been done by Marina Amaral a Brazilian digital colourist who specializes in adding colour to black and white photographs, “breathing life into the past”. You can see examples of her work in her portfolio or watch an interview in which Marina talks about her work, which is also featured, in the video below.
In progress….