When you quilt, be it machine, hand or free motion, what color thread do you use or should use? Do you use white or try to match the color of the fabric that's being quilted? Which is best?

It depends on the look you want. If you match the thread to the fabric, it does hide mistakes better and gives you a textured look. But, it is hard to see while quilting. Contrasting thread is easier to see, and the quilting design will be more pronounced, but mistakes will be more noticeable. Many people quilt with an off-white or cream color I think. My favorites for the top are variegated threads.

I tend to match the bobbin thread to the back. But, I'm doing much better with my quilting, so I'm not as afraid of the mistakes in stitching showing as I used to be.

Whichever color you like best to quilt with is the best answer. It's your quilt, you do what you want.

depends on the quilt and if i want the quilting to stand out or blend in- every quilt is different- every quilt gets its own fabrics- patterns- quilting designs and even threads.

I match the bobbin thread to the backing fabric. The top I choose whatever color looks the best.

I rarely machine or handquilt but when I do I use Superior Threads Bottom Line - it doesn't matter what colour as it disappears into the cloth
I usually use a light one for a light coloured top and dark for a dark one

I also look at the back and to see what color would look best. Most of the time it turns out to be a very neutral color.

If you want it to show, use a contrast. The higher the contrast, the more the design (or in my case, the booboos) will show. The quilt on my frame...3 shades of purple (light to dark) and off white, the owner picked a soft green. You can see it, but it does not jump out at you.Love it!
If you just want the texture, match it to the top. I learn something from EVERY quilt I quilt...

I always use an off white hand quilting thread. The one quilt I did by machine I also used an off white. But I don't often use very dark colors in my quilts.

I have only 1 quilt under my belt, but had happy results with 2 threads from Superior Thread; 'So Fine' in medium-off-white on rainbow color quilt top, and 'Bottom Line' in white on black/white print back. In addition, I think it helped going with a finer weight thread on the multi-color top...a thicker thread would have been too dominating and the light neutral offered a little less contrast.