I just about always use the same color thread in the needle and bobbin. No pokes on the top that way. I usually also pick a somewhat textured fabric for the back. Once in a while I will just use a grey or cream in the bobbin depending on the fabrics in the top and bottom. I use a 50 weight thread usually (usually so fine) which really blends in fairly well and is not the noticeable. I do not make quilts with a lot of plain space for showing off my quilting.