I named this Coulda Bought This Blue because I am pretty sure I ended up making something I either already own or could go to the store and buy pretty easily. Still, it's interesting to see how things combine. I used an old Sally Hansen Advanced Hard as Nails called Balance and Wet 'n' Wild Wild Shine French White as my transformative ingredients.
Balance is a pearly shimmer with a blue flash that I thought would work well with the Borghese.
I poured Mezzanotte Blue into an old L'Oreal bottle until it was about three quarters full, then added Balance until it was almost entirely full. That didn't look quite light enough to me, so I added five drops of French White. After mixing that up, it still didn't look light enough, so I added five more drops of white.
In normal room light (above) the shimmer is not too obvious; in brighter light (below), the blue flash from Balance pops out a bit more.
Here's the franken compared to Mezzanotte Blue alone and Balance layered over Mezzanotte Blue:
While this is not the most exciting color in my stash, I did achieve my goal of making Mezzanotte Blue into something that doesn't turn black on me in most lighting conditions, so I'm happy with it.