try using a disposable pipette to place the layers in?

I'd have to use medical tubing and a syringe to get it cleanly into the tip and unless I switched to transparent block molds I'd be doing it blind. And the resultant horns would still end up weighing more than the originals. :/

TBH any option for doing horns like this will be a massive arse-ache. It's vastly easier to just paint a set of single-colour ones. And about an order of magnitude cheaper and more reliable.

Ouch. It wasn't this bad on the candy corn troll horns.

It's probably possible to avoid on 3-shades, but gets exponentially more likely you'll screw up and ruin all the work so far. Far easier to just do a yellow pigmented horn (for homestuck) and paint the other two bands on. More controllable too.

I didn't even try casting in colour with my set, I just acrylic painted them haha!