I can't comment on Feldon, but I take your meaning. My sense of things is that we probably agree on the nature of the characters in R+J (especially Mercutio—I mean, Queen Mab, my goodness), but may differ somewhat in our interpretation of the colors. In my view, Red is well capable of breaking stuff on its own, and the lovers' behavior is well explained by Red alone.
To be sure, the aesthetics of R+J dip heavily into Black. Juliet in Act IV Scene I, For instance:
O, bid me leap, rather than marry Paris,
From off the battlements of yonder tower;
Or walk in thievish ways; or bid me lurk
Where serpents are; chain me with roaring bears;
Or shut me nightly in a charnel-house,
O'er-cover'd quite with dead men's rattling bones,
With reeky shanks and yellow chapless skulls;
Or bid me go into a new-made grave
And hide me with a dead man in his shroud;
Oh my. However, the lovers' motivations are pure Red, and my feeling is that their means are Red as well. It's not as though Juliet schemes up the sleeping potion plan herself (which might suggest some Black to me); Friar Lawrence has the idea and Juliet seizes on it because she's love-mad and impulsive. The potion is just there. If she could "borrow" daddy's corvette and go marry Romeo in Vegas, she'd do that.
Does Juliet have Black because she stabs herself out of heartbreak? To me, that's a pure Red response: this is how I'm feeling so this is what I'll do. Black, a more sober color, might help her stop to think about her agenda, how to get what she wants. Juliet hasn't got an agenda, though. She just can't bear this feeling and so takes her own life.
Perhaps you'd say that Juliet stabbing herself is a sign of Black ruthlessness? Her behavior there isn't related to ruthlessness in my opinion; it's about having her coping mechanisms overwhelmed, about lacking the experience and maturity to put what she's doing into context.
As for Romeo, I might see a stronger case for Rakdos in his case, but even then:
The time and my intents are savage, wild,
More fierce and more inexorable far
Than empty tigers or the roaring sea.
Guy is like a bull elephant in musth. Seems Red to me.
It's nice to talk Shakespeare on this sub, by the way.