Blood is the corruption of Water through Dark Magic
Candy red blood imits the most oder of iron to an overwhelming degree, while black blood is the stickiest & thickest with a faster clotting speed. Deep red blood is the more neutral variant, though it's the easiest to affect others' blood systems (that doesnt mean they other two variants have a low chance, its just since deep red is the closest to normal blood that makes the manipulation of another's body easier)
With higher mastery, any dragon/drake can suck and use others' blood from the capillaries closest to the surface of one's scales (which is understandablly painful), and at around Savant and over a dragon/drake can rupture blood vessels, cause brain aneurysms and rupture organs withough having to touch another creature
Blood dragons can use puddles of blood to teleport around (so these dudes make a hella mess when they get into fights)
The percentages on the varients indicate an estimated amount of dragons with the Blood element (a bit tricky to aply to those with quirks). So out of all Blood dragons, 50% have the neutral Deep Red varient, 40% have the Candy Red varient, and 10% have the Black varient.