So I got to collaborate with Joseph Arruda on this awesome piece that he drew. I've been following his work for years and it's truly an honor to get to work with him. Go check out his stuff here. This is a color process of what I did in Photoshop.
This is the line art by Joseph = awesome.
First I just lay down the flats. I usually use muted colors to work as a mid tone.
On this step I added shadows on the ground, picked a background color and whitened some of the line art on certain spots. I also created a copy of the flats and blurred it to give it a very subtle dark 'glow' around the characters and moved it under the flats layer.
Here I started with highlights using a soft brush, picking a light source coming from the top. Also added a lighter color to the ground and just played around with a textured brush for the background.
More highlights to the rest of the characters and added some shadows as well.
Now it just consists of adding more details everywhere. Added yellow lights coming from different parts of the robot, some red reflecting off the glass surrounding the robot's head, brighter highlights on certain spots and subtle lighter colors on the darkest parts.
And this is the final which consisted on adding details to the light reflecting off the glass, and making the robot look like it's been through some rough times by adding dents, scratches and rust all over the place.