Clear purple dilemma

going for black, that appears purple when light hits.
(Barely purple, mostly black)

Not sure clear over black looks.

Maybe try a clear blue over a solid red base coat, or vice versa? I just tested it on a scrap piece I have lying around and got a sort of purplish color, leaning more towards a reddish purple, though that was brushed on, might work better with an airbrush, but really have no idea. You could also try mixing a regular purple with transparent clear and see if that works, you may have to tweak the ratio of paint to clear coat to get the desired effect. Just a suggestion.

It usually turns a weird blackish color.

That's disappointing D:

What if you add regular Clear to the mix? It might dilute the color so it looks more purple instead of like concentrated darkness.

Testors and Tamiya both make acrylic clear blue and clear red, you can mix those to get clear purple.