A brief explainer on my setting's mana regarding its form:
First off, color. Natural mana appears as a sort of vague mix of colors, with occasional pastels of different colors jumping out and very rarely forming darker hues. When someone channels mana it passes through their soul and gets sorta... tinted by it, taking on a single color typically related to the individual. These colors aren't unique but some colors are rarer than others, they don't really mean anything either they're just. your spells take on that color. that's it. beings formed entirely using spells typically either take on the caster's mana color or some shade of purple.
Now, mana isn't usually a physical substance when encountered. Most often, it's just sort of immaterial energy that permeates everything. There's hot spots with lots of it and cold spots with very little, and Earth just so happens to be a big very strong cold spot.
When mana is made physical without just becoming normal matter, it usually acts like a crystalline solid. However, it can also be made to manifest as a liquid or gas. It has density and mass based on the amount of mana put into it, you can technically put an arbitrary amount of this mana-matter into a single space but that's generally considered a bad idea. The standard convention for storing it as physical matter is to give it a density of around 20g/cm³, which is a little higher than gold.
Also, one last note - just like how mana can turn into regular matter, regular matter can be turned into mana. As can energy. Mana is basically the physics equivalent of "generic stuff" in that it can become Literally Whatever and anything can turn into it
