I've been working on and off on this, but I had to wait for the package from MWG to come in order to put the tube in the gun. I couldn't use green tubes on blue necrons

The tube also gave me the idea to make a crystal terrain for the necron's base. Now the blue color is justified for their armor.
The base was made with a green stuff support in which I've stuck some short blue transparent tubes. After that I've glued on some sand, painted it black, and brushed it Mordian Blue/Enchanted Blue. The highlights are made by painting thinned ice blue/vallejo deep sky blue painted in the green stuff's cracks.