I noticed the color changes [on the sparks effect]. What is that?
TL;DRThe sparks change color because particle color is driven by a gradient over the particle's age, with randomization to avoid uniformity and an alpha curve that fades the particle out as it cools.
So this is particle color over life. The reason here is the hotter it is, the color is going to change based on the heat of the thing. Lots of hierarchies as well with particles. We're not just limited to one. But we've got a colour gradient here. So this is the particle age curve. So the life of this particle is specified here. So each of these individual particles is going to last for three seconds. I've actually got a random value on it as well. Without the randomisation, everything starts to look a lot more uniform. So if I just strip that back, you can see it's all looking very uniform now. And changing the color over the age, you'll see that if I increase it so it's blue for basically half of its life, then it starts to go orange. We've also got an alpha curve on it as well. So actually, while it's changing color, it's also becoming less and less opaque until it gradually dissipates into the air.