Description/Explanation of Issue
ETC has three variants of ColorSource Fixture arrays. The Deep Blue Array contains an Indigo emitter. With a Deep Blue fixture used in Direct mode (must be running v1.3 or higher to set to Direct Mode), you can set that Indigo emitter to full and achieve an effect similar to what you would see with true black light.
The ColorSource Standard array contains a blue emitter and cannot achieve the desired effect, and the Pearl Array does not contain any color emitters.