Originally Posted by Marin
If everything turned blue you wouldn't be any better off than before.
Does fuel on an engine block or injection pump turn blue while the surrounding metal reflects no light at all?
I just reread your post and looked at the photos and see what I think you may be seeing and I should have (no pun intended) highighted ...
The fuel will glow but nothing else around it unless that material itself will fluoresce, which most things don't. A drip or run of diesel will glow but the metal around it won't.
If the paint color is close to the color of the glow it can be very difficult to see. That is why the tracer dye helps because it makes fuel stand out from any normal background.
The blue saturation shown on my picture is because the only illumination was from the UV light. The paper towel glows bright white in UV, the fuel was glowing bright blue and the transmitted light made the surrounding white paper and the background appear blue.
The camera chip may also be more sensitive to UV or blue spectrum light than the eye so that may increase the blue saturation but you are the expert in that area, not me.