Is there a property of the particles like "Amount", I saw it in other editors, it gives brightness to emitter?
hmm I dont really understand. Since there is no Gamma filter in Starling Stardust does not have it either. You can play with the blend modes to have them look different.
How I can change color of particles overtime?
There is no such action currently but its easy to code one, just make an Action that sets the colorR, colorB, colorG properties of the particles. For an example of a custom action check to follow mouse example on Github (I recommend this solution).
Or if you dont want to code a custom action use a sprite sheet as particle graphic where the graphic changes color in each frame.
Btw I am planning to make a "change color over time" in the near future. I just have not really ironed out how exactly you would be able to change to color. One way would be like how you define gradients in Photoshop: I display a horizontal bar where you can click and set colors. And a textfield where you can set how much time it will take to loop trough this color bar? Or add a setting where it loops trough it in a fixed time/loops trough it based on the total life of the particle?