I have used a 100% cotton varigated thread for hand quilting but it was definitely marketed for hand quilting and is a 35 wt. It is also a high contrast to my quilt going from lemon yellow to white. I have posted pics of this WIP before but I will post one again in case you missed them. Be careful using a high contrast dark thread against a light backing though. For whatever reason the dark against light is much less forgiving than light against dark. Some one posted once that light thread on a dark back looks classic but sometimes dark thread against a light can end up looiking "spidery".