Ok so I was wondering if it was possible to add a red tinge to all of these colours, but I don't won't to go into the node editor and change each one individually to have a red tinge. Is there a way that I can add a red tinge to all of the materials in one go? Essentially have some sort of master control over these 3 colours, so that if I add a colour to one of the materials it will also effect the others.
This is best done with node groups. Add a "main color" group that outputs a color to tint with. Incorporate that into the material nodes. Then, whenever you change the group, all of the nodes get the new color update.
As far as automatically adding the groups, it would be much harder (although not impossible), and it would require a good bit of python programming.
Just an idea, don't know if it's workable for your blend: set-up a light/lamp and give it a red colour.
If there are objects in the scene you don't want a red 'tinge' to, then I believe it's possible to make those objects ignore the light.
This would then be a 'global' overlay on top of all materials that receive the light.