nameplate threat border for default blizzard small plate

[jessica]

I like the default small blizzard frames, but it has no threat indication, and the only addons out there that alter this, is by changing the whole color of the nameplate.

I want a different thing, you know when you have a target on default blizzard nameplate, there's a gray border that appears, I want this gray border to change to "yellow" for low-threat, then change to "red border" when I have aggro.

how can I do this, thanks.