Apple Motion 3 - Manual (Page 746)

746 Chapter 8 Working with Particles
The resulting image should look approximately like this:
Note: If necessary, disable the original Spark12 source layer.
7 Next, change the color of the particles generated by the Spark12 cell by doing the
following:
a Choose Colorize from the Color Mode pop-up menu.
b Click the color well in the Color section of the Inspector and choose a light red color
in the Colors window.
c Close the Colors window.
All particles generated by that cell are now red.