Digitals don't have the blood types we humans do. Their bloods, however, help determine their abilities and elemental power.
Creature Type Edit
Creature blood can be found in more animalistic Digitals. (Obviously) This is actually quite sensitive blood, so Digitals with Creature-Type tend to feel pain or tickle easier.
Humanoid Type Edit
Humanoid Blood is a lot more like our blood. It's quite stable, and moves faster than Creature blood.
Elemental Effects Edit
Here's how blood can determine elemental power.
Digitals with the Fire type have very warm blood. They tend to run fevers if they fight too much. It also allows them to have more flexible tempers.
Digitals with the Water type have cold blood. They must move around constantly to keep their body temperature normal.
Digitals with the grass type have an oily feel to their blood.