Adding another gas was relatively trivial lmao. Technically I realized partway in that I was somewhat jumping the gun but eh this is okay.
I realized partway through that the fact I was tracking flow velocity is a bit sketch when multiple gases of different molar masses are interacting, so I replaced it with momentum. Pretty much heavier gases should influence lighter gases more, but lighter gases will move much faster.
The second gas is visualized as green on the shader, and is like fake O2. The only difference between the gases currently is a higher molar mass(O2 would be 16x heavier!). The only noticeable difference in how the behave at the moment is that the O2 is denser, thereby being accelerated slower and having higher momentum.

Next up should be temperature. technically the temperature of a gas should change as its pressure changes. Though the changing of temperature will also effect its pressure, so that might be a bit hard to balance. We’ll see!