Changing particle colour (alpha) at runtime

I have looked through various other questions on this topic, but none of the solutions seem to work for unity 2017.2.
Q: How do i change the colour of existing particles (especially the alpha channel) at runtime?

this is how i try it now:
private IEnumerator FadeOutParticles(){
ParticleSystem.Particle[] particles = new ParticleSystem.Particle[myParSystem.particleCount];
myParSystem.GetParticles(particles);
for (float alpha = 255; alpha > 0; alpha -= 255*Time.deltaTime)
    {
        for(int i = 0; i<particles.Length; i++)
            particles*.color = new Color32(100, 100, 100, (byte) alpha); //deprecated?*

yield return null;
}
}
other questions on this site suggested using
“settings.startColor = new ParticleSystem.MinMaxGradient( yourColor );”
but that does not work for existing particles. Or:
particles_.GetComponent().material.color = myColour*;*
and that wont be good either as it changes the material instead of the color of the particle itself._

The color of individual particle after being emitted is not gradient, just give it a straight Color32 value and you’re done.