credit to the artist ADAL
colorist by 
Colouring comic setup. After finishing the digital inking process, ensure the position of the layer, just like the picture above. Create 2 layers with one normal layer for the coour at the bottom and above is the multiply layer for black and white outline.
Click on the normal layer. This layer you can colour it with flat colour by using the paint bucket tool. If there is a break in the line, use a normal brush to close the gap by using the colour of choice. Then you can use the paint bucket again. I usually use thick colours within the middle range colour for my process for overlay layer to make it shine.
Once the flat colour is finished we move on to the lighting and shadow chapter. You can see fro the picutre above how I choose laywer overlay for my lighting and for the shadow I use multiple layer with the colour of light blue.
Once all the final colour for my character is completed, I will focus on the background colour. For the lighting and shadow I will use the earlier process that is to highlight for overlay and multiply for shadow.
Now we can see the detail of the work that I have just finished.
It is quite common for the art work to be prepared by one artist and the colouring to be completed by another. Somehow the difference in interpretation of the work do create amazing result.
credit to
@zomagic