I have found a nice technique to add colour to the greyscale texture.
The usual multiply layer makes the textures look dirty and dark. The new technique I am using involves adding colour by layering overlay and soft-light layers.
The best thing about this technique is that allows the refinement of colours long after they have been applied. Using layer masks to apply them also makes sure that the colour is consistent across the whole texture. This was quite annoying when you complete a metal panel and have to repeat the process in a new one...."How did I do it?.....this method is perfect for repeating.
Other good point is that the materials can be repeated in different textures by copying the layers and reseting the layer masks....
I am very happy with this new process. This shows the core module being coloured. The red-brown color is the starting base over which the rest has been layered.
I have to give all credit to Stephen Flack as I learnt this technique with his tutorial.