How they could look on envelopes

As I'm planning on printing on see-through vinyl for a (hopefully) interesting effect when applied to envelopes, I had a little play with the multiply setting to see how it would look like if the envelope's colour creeped through the 'white' transparent areas and changed the image.

Original, or how it would look on white vinyl

How see-through stamp could look like with envelope colour creeping through ^^

I think the added colour just finishes it off a bit more, with the off white. Obviously, some envelopes are white, but I like the idea of the stamp  being different depending on what envelope you use.

If I do end up printing on white, I'm going to add this off-white colour, I prefer the overall aura of it compared to on white. It's a bit softer and suits the kind of retro 50's vibe I'm trying to go for with the "Ice is so last century!" tagline.