I dont have that specific washing machine but on my front load washer (LOVE LOVE it! it's my second front load washer) I would wash it cold to hot (mine has a stain-something cycle which basically starts out with cold water and gradually heats up the water but it takes 2 hrs instead of 1 hr to wash. And in AZ, all my water is hot anyhow! I dont typically use this cycle but do love using the pre-wash option. I find that I have to use powdered for the main wash with using the pre-wash option as liquid will seep in with the pre-wash leaving none for the main wash.)
If you have particularly poopy/stainy diapers, then I would wash with cooler rather than hot water. My husband swears by Tide (he brings home manure covered coveralls). Even so, there still are stains that slip through. The most important things in preventing stains is to NOT dry it without having washed the stain out completely first as the heat sets the stain.
For dirt/poop stains, washing with warm water is fine. For blood you soak first in COLD water, then wash in hot. Grease will not come out in cold water. Generally, for anything I think you are safest in starting with cold water (pre-wash or pre-soak is fine) then washing in warm/hot water.