Health Bar Mods

[Badace]

First off I have never done any Mods what so ever.. in fact I have no clue where to start. So please post a step by step for a newb.

Im looking to modify the point at which the health bar changes color... currently the bar changes color from Green to Yellow at I think about 80% of your health... I want this color to change at about 90% of your health..

Is there anyway to do that....

P.S. Ill also be changeing from Yellow to red settings as well.