Nope, it's just the HUD texture that was given a green color and it makes darker areas more noticeable in-game, it's just a normal consequence to our eyes, there's a deeper scientific reason as to why green is used in real life for NVGs. The effect of the green on the HUD texture also depends a lot on the quality of the screen panel on which you play games. On my end, without cockpit, I couldn't see the terrain on the horizon at night with the realSKY mod. By enabling the cockpit, then I could distinguish the terrain from the sky thanks to the HUD's reworked texture.
There is no way to add such a FLIR shader effect to the 3d model of the cockpit. Hell, we don't even have a proper FLIR shader in the game for the DTV in cockpits, which is the cheap reason why TK made nights unrealistically bright. We've been there already, we've been modding the game for two entire decades (considering SFP1 days) so we know all about the engine limitations, there's nothing new to discover about it. The only realistic solution (apart from using Unlimited Effects, thus having TW's post processing shader kick-in all the time) is to use a shader injection method like Reshade, but that one eats a lot of resources and can decrease FPS by a lot depending on the system on which you run it. I've been looking for lighter alternatives but nothing good that works in SF2 so far. All that is needed is to reproduce the shader done by simonmiller416 for use on such a shader injector (the TW .FX shader cannot be re-used as is, the shader injector usually requires its own syntax and/or language).