Thread color
 

Red & black quilt - what color thread do you use?

for piecing? black or red
for quilting? gray

That's a hard one. For me, it depends on whether the quilt "reads" more as red or black or white. Since I'm a bold quilter, I'd probably choose red.

I'd use gray for piecing.

For quilting, it depends what effect you're trying to achieve. If you use red thread for quilting, you won't really see the quilting on the red pieces, but they'll pop on the black. The opposite is true if you use black for quilting.

If you want the quilting to be relatively quiet vis a vis your piecing, use gray. If you want it to call bold attention to itself everywhere, use the brightest white you can find.

Grey for piecing.
Both red & black for quilting as I tend toward custom quilting, rather than pantos/all-over designs. If you plan to do a repeating design that runs across both the black & the red fabrics, then it would depend on how confident I was with my quilting design & whether I wanted the quilting design to be the star. Your best bet for getting the quilting to "blend" is probably to pick a very dull red cotton thread in a 50/2 or 60/3 weight. The other option would be a very dull green, since that's red's direct complement & would end up reading as a rich grey, except very close up.

If you want the quilting to be the star, I'd pick a 40/2 white cotton so it shows up equally on the red & black ... although, you could pick either a matching red or a matching black and it would blend on its match & create an interesting pattern on the other color. So many beautiful choices, you really can't go wrong!!!

Picture would help form an educated opinion. In general, if you want to see the quilting - use grey or another lighter neutral. If you don't want to see the quilting, use a smoky monofilament or black on black/red on red. Or use a variegated red-black with a short repeat and get the random look.

I usually puddle a bunch of thread on the quilt top and see what looks best to me. There is no right or wrong - just preference. I might even try gold on your red and black quilt, or silver. Sometimes I use a pale blue on a top that has a lot of white, just so the quilting will show up everywhere.

It has not been pieced, just planning ahead. Thanks for the advice. i will have to get some gray thread.

Why not yellow!