LIGO detects most massive black hole merger to date

We can't REALLY answer questions about what's inside the event horizon, but some real work has been done on what BH mergers look like, though even that as I understand, is extremely difficult model.

https://m.youtube.com/watch?v=5AkT4bPk-00

What are the waves of gradient colors, gravity?

I'd guess its the weyl scalar w4, which is generally used to extract gravitational waves

These kinds of simulations inherently cannot model the singularity accurately whatsoever. At the singularity, the numerical technique used becomes knowingly invalid

In fact, the entire interior of the event horizon is actually physically invalid in these simulations. The formalisms used trap the errors inside the event horizon, as the errors turn out to be strictly causal. And because of that, theoretically they can't escape

Of course that analysis breaks down in the face of discretisation, so errors tend to leak out a bit under low resolutions, so you have to handle things pretty careful. Either way, you shouldn't draw any conclusions about the interior

Source: I've done a lot of these simulations