The millions of simulations were spread across the various possible combinations within this framework. As a whole, the results form a rough map of all conceivable outcomes, like a vast tapestry woven from the threads of initial configurations. This is where the isles of regularity appear.

The colors represent the object that is eventually ejected from the system after the encounter. In most cases, this is the object with the lowest mass.

"If the three-body problem were purely chaotic, we would see only a chaotic mix of indistinguishable dots, with all three outcomes blending together without any discernible order. Instead, regular 'isles' emerge from this chaotic sea, where the system behaves predictably, leading to uniform outcomes—and therefore, uniform colors," Trani explains.

The full paper is here: https://www.aanda.org/articles/aa/full_html/2024/09/aa49862-24/aa49862-24.html

From what I gather, they're looking at the trajectories of the first object ejected from the system over all of the simulations, and they're finding that:

If the 3BP was fully ergodic, we should see a mix of colours everywhere, but instead we observe four large regions of uniform colours, two large ones at ι ~ 80° and 260°, and two small ones at ι ~ 175° and ι ~ 355°, that we term regular islands.

https://www.aanda.org/articles/aa/full_html/2024/09/aa49862-24/F3.html

All of those colors on those images are dots, each one representing the outcome of a simulation. The large single-colored areas shouldn't exist if 3BP were truly chaotic and unpredictable. Furthermore, you can see some "finer structures that look like narrow stripes."