In the map im making (Xero Bound), i used the the stats below for a Zergling and the glowing health was orange and black. The stats work for all other Zerg units and the Mineral Chunks. In all other maps ive seen with glowing health they are black and blueish. This looks pretty cool. Maybe its because im in ash world terrain? when its dont ill post the map up so that you all can see. It'l be a while tho srry.
Properties:
HP _4 l _____1
Shields :_____0
Armor :_____0
[MOVE]Xero Bound:
[progress]55[/progress][/MOVE]
Im not sure, maybe its the terrain that your using for it...try using different terrains (Ice, Jungle, Ash, Twilight, etc.) Mayb it makes different health
EDIT:

i figured it out! ash world terrain uses that type. try another terrain if you dont want orange and black
If you use sprites (so that they have the repset health over 1 if you want), they wil change color everytime you attack them. I've seen yellow, oj, green, blakck, blue, inbvisible, pink, purple, mixtures etc. Very strange. Is there a way to turn a unit sprite into a unit without doing disable/enabke/enable thing? If you could, it would be alot easier to have different colors by setting the base HP.