Using Photoshop to Colourise Options

[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!!

[JohnVV]

it really depends on what is being colorized
combining a set of 3 Red, Green, Blue images into a color image
( this has been done scene the mid 1800's )
for example this photo gallery from 1909 Czarest Russia
http://www.wired.com/rawfile/2014/03/proku...-photos-russia/

where a black and white images using a
1) red filter
2) green filter
3) blue filter
are combined into a single RGB image

from a different post about the MSL
0229ML0010620000106079E01_DRCL.IMG
that is a rgb image but i can break it up for an example
-----red ------ green ---- blue


this is for Gimp 2.8.10
open all three red,green.and blue images
from the red click on
Color / Components / Compose


set the red layer as the red image
set the green layer as the green image
set the blue layer as the blue image

and you get this







The other type is ...
converting a black and white image that has NO!!!! color data

for example this fractal noise made Planet DEM


and colorizing it to this


this is more an ART FORM than a step by step
There is for a now gone tutorial ,still on the internet archive
http://web.archive.org/web/20130625110058/...=21&t=16089