For those who might have familiar issue
If you want to have each particle in the same colour as the original PNG independent of its background be sure to set the following parameters in Particle Designer
Blend source: GL_ONE
Blend destination: GL_ONE_MINUS_SRC_ALPHA
Start color: white (100% opacity)
End color: white (100% opacity)
Pay close attention to start/end color. I didn’t set this at first and it was causing me issues.
Hope that helps.