Soul campfires do not emit ember particles

Since it is a different type of fire, it should not emit the same orange particles the regular campfire emits.

Then shouldn't it emit blue particles then?

Exactly

I think it may be worth revisiting this issue. The particles.png file in Bedrock Edition actually contains a soul variant of the lava particle (see MCPE-121516), which logically would make sense for use in a situation like this.

I would argue this is a feature request, especially when the Bedrock counterpart was resolved so.