the effect that the character does when his mana is at 200, it's like a blue glow, Leinfors, and thanks for answering
Terraria Community Forums
Leinfors
If I am correct, that is not a sprite, it's a dust effect. And while it may be potentially possible to texture replace the entire dust sheet, I suspect you will not be able to get the effects you are looking for, as a lot of the stuff controlling dust visuals is code-side.
They are found in Images\UI\PlayerResourceSets\FancyClassic, and if you mean the "inside" of the star, it is Star_Fill.png.