Hi Ya!
You can color poly a couple of ways... I tend to use chalks.
Stamp your Stazon of course and when dry lightly chalk the image. You could use markers... however, it won't ever dry... so I am not sure how you would keep it from smudging before you sealed it...
I would assume that you could also color with the chalk pads. And I have used fabrico markers and "colored" with craft pads... just remember that the color intensifies as it shrinks. Hope it helps!
Kim