How can I preserve color in a 2-ply?

On purlwise's blog, she asks: I have a painted roving; if I make it into 2-ply sock yarn will the colors look ok?

My suggestion is that one color-play you can do as a 2-ply is to split the roving along its entire length (awkward, granted) and fill two bobbins with each half. If you're spinning the same thickness/grist on each one, or close, then you'll get long sections where same-overlaps-same, and "edge" sections that heather two colors together in between switch-overs.

Or, if splitting the length doesn't float your boat, you could find the repeat in the dye on the roving and split it there, instead.

Alternatively, consider Navajo plying to preserve the color changes.

I'll try to dig my pair of fingerless gloves out of my sample-bucket for a photo shoot; one is a 2-ply done as described here, and one is a Navajo ply. All you have to do to confirm the adage that a 3-ply is rounder yarn and a 2-ply is flatter yarn, is put these on. The Navajo (3) ply is squisher/firmer, the 2-ply is flatter against the hand. And actually, in gloves, flatter against the hand is a good thing between the fingers!