Victorian Railway Diesel Blue.
 
A black undercoat is recommended to recreate the very deep rich blue ex Works. In addition a gloss coat may be added to increase lustre.
 
The paint colour is scaled to represent an in service loco with paint starting to fade. The paint is very flexible, try adding a dot of white to fade the colour further, combined with a flat or dull clear coat a variety of effects can be created.
 
There is more to colour than just what the label says on the jar...!...