You can use any color thread you like. I am working on a project now and am using variegated thread that goes from deep yellow to white in subtle graduations. The quilt is predominently black.
I prefer to hand quilt with a heavier thread (35 weight). With thread the lower number signifies a thicker thread so 50 weight is finer than 35 weight. I actually break the rule and on average I use a length of thread that is longer than my arm. When I spin it off the spool I go the entire length of my arm and across my torso so I am probably using a length about 30". I use beeswax (DH keeps bees so I have a good supply of capping wax which is the best quality and smells so good!) A little wax goes a long way. I also make sure I move the thread regularly so it doesn't fray and break at the eye of the needle. I never have problems with knotting or tangling. I attribute that to the wax and using a heavier thread. If I forget to regularly slide the needle down the length (I do it every other needle full) I have had my thread fray and break right where it was in the eye.