Bonded Polyester Thread is the go to type of thread you want to use for anything Heavy Duty! From Upholstery to bag making, you won't find a better type of thread. 

Variegated threads are Tex 45 and should be used with a 100/18 needle (Top stitch or Jeans) while solid threads are TEX 35 and should be used with a 90/14 needle (Top stitch or Jeans).