This is sorta inspired by the questions in the FotF about more geological features. I looked through several threads and found mostly stuff about hot springs and eruptions. So let's look at the other stuff.
Volcanos in the game are right now mountains with a magmapipe.
It would be interesting to see more volcanic activity in the game:
* different volcano shapes(these are influenced by how the volcano came to be).
* Cryptodomes, Shield, Cinder cones, Stratocones.
* Volcanos with multiple magma tubes.
* Volcanos with broad tubes, or really thin ones.
* Really big caledras in which there's the tubes or lakes.
* underwater and glacial volcanos
* lava lakes
* Dead volcanos.
* Vents filled with volcanic gasses.
* Geysers, mudpots and hotsprings.
Volcanic activity could be influenced by magic, such as, of course, eruptions, but also in a fisher king like manner, where killing the dragon might actually kill the volcano they're in as well.
Now how does colored fire come into this? Well, colored fire on Earth is largely caused by gasses(white fire is the highest that is possible on earth, we know of stars that burn blue due what is suspected to be temperature, but such high temperatures aren't possible on earth as far as I can tell). And volcanos do indeed sometimes burn such gasses, such as the case of the
Indonesian Ijen volcano(s), which has blue lava and flames due to sulphuric content.
Looking at the wikipedia page for
pyrotechnic colorants, it seems the easiest way to deal with colored fire is to just add a tag for fire color to the materials, with it defaulting to red. Doing it this way will also ease up on any future attempts at implementing decorative fireworks.
Colored fire in turn can also be colored due magic, think Malificent and her green fire in Sleeping Beauty, and depending on how consistent the magic system is able to make symbolism it can provide valuable information to the player.