Here is an interesting image from Donald Mitchell on Twitter. It shows the average colour of planets and moons in the Solar System.
It would be interesting to do the same for exoplanets. Here is Vivien Parmentier showing possible colours of hot Jupiters, depending on their atmospheric composition and temperature (Credit: NASA/JPL-Caltech/University of Arizona/V. Parmentier):
Here’s a nice graphic by Sean Raymond illustrating different scenarios for the formation of exoplanetary systems, one leading to “Super-Earths” and the other to gas giants. The work is explained more fully on arXiv.
The paper’s figure caption includes:
Left: Evolution of the “breaking the chains” migration model for the origin of super-Earths. Embryos within the snow line are entirely rocky and much smaller than those that form past the snow line, which also incorporate ice. Presumably ice-rich embryos migrate inward through the rocky material, catalyzing the growth of purely rocky planets interior to the ice-rich ones. Planets migrate into long chains of mean motion resonances, with the innermost planet at the inner edge of the disk. The vast majority (90–95%) of resonant chains become unstable when the gas disk dissipates. The resulting planets match the distributions of known super-Earths.
Right: Evolution of the planet-planet scattering model for the origin of giant exoplanets. Several embryos grow quickly enough to accrete gas and grow into gas giants. They subsequently migrate into a resonant chain without drastically affecting the orbits of nearby growing rocky planets (or outer planetesimal disks). After the disk dissipates, the vast majority (75–90%) of giant planets systems become unstable. The resulting systems match the correlated mass-eccentricity distribution of known giant exoplanets.