Hi,
Correct me if I'm wrong, but, as I understood, you would like to spawn a particle with random color on creation?
This isn't implemented in GameMaker's built-in particle system but can be achieved via a line of code like:
part_type_colour1(global.Snow_Part, c_white);
What I can do is to allow to disable the color blend for 3 colors and add custom Randomize checkbox for 1 color.
Is this what you'd like to see?