There is one called betcoin.ag that has red trust users in there.
But believe they were given red because they are in that campaign already when they received it.

Why should people give red trust to the participants of betcoin.ag signaoture campaigns?
Do they break the rules of this campaign? AFAIK only betcoin has the red trust because of the recent issue to their site but I guess betcoin do his job to put back his trust in this forum.
And that signature campaign is one of the oldest campaign here.
And for OP if you want to work with signature campagn that acccepts negative trusts you can always check the altcoin announcement for some campaign, because there are also accepting there but only if the DT will not exceed below -2 else I'm not sure if they still accept you.