This has been asked and answered before:

Recently (today) I first noticed someone people have positive trust that is black (not green).

Is there any significance to this?

It's black if it's positive but lower than 5. Light green between 5 and 14. And dark green when it's 15 or higher:
https://bitcointalk.org/index.php?topic=1066857.msg11433784#msg11433784

And of course it's red if it's lower than 0.

And how much i trusted feedback is worth?

you cant buy trust if thats what youre getting at.

i have an alt with +1 positive from OgNasty and it's black

None of them