[X] My Assistant

[algorithm]

I for one look in wonderment at the work of Damia and others. Being a curious soul I also want to know how they do it and also have a go at colourising myself.
I have searched through Google trying to find tutorials on colourising but the results tend to be in the realms of changing red cars into green cars etc.
I have also searched for colour mapping, gradient mapping...the list goes on!
I have come to the conclusion that I don't know what I am talking about and therefore don't know what question to ask.
Could someone please point me in the direction of a good resource on colourising greyscale images using colours from another 'reference image'. (Is that the right question?)
I have Photoshop cs4, cs4 extended, cs5.1 and cs6.
All this software and no knowledge.....it's getting embarressing!!

[algorithm]

The colourising of an old black and white image to make it look as though it were a colour image is an artistic labour of love.
I am not a lover of labour, neither am I an artist. My eldest twin daughter however, is a bit of a budding artist, so I will show her this thread, I think she will love it.(It might even get her away from social media for a while!)
A step by step tutorial is an abhorrant idea, a general methodology which I can adapt is what is required, I think I need to go down the custom gradient route.?
Thanks again for all comments.