How to make a particle system evenly lit?

I’m currently working on a simple blood splatter particle system to use in a game so that when a character dies, blood splatters in a short burst over the screen and then fades away but even though the look is kind-of-ok-ish, it’s only visible on dark parts of the background and almost completely invisible on the light parts. Why?

Here is how I set up the particle system:

And here’s the problem in action:

Try a different shader. Maybe a Transparent Unlit.