Well, this thread hasn't been flooded by such requests, which means either that other people already know, or know how to find out. You are the only person here who claims "authority" on such matters while admitting you have no clue. So indulge yourself:
In WTO terminology, subsidies in general are identified by “boxes” which are given the colours of traffic lights: green (permitted), amber (slow down — i.e. be reduced), red (forbidden). In agriculture, things are, as usual, more complicated. The Agriculture Agreement has no red box, although domestic support exceeding the reduction commitment levels in the amber box is prohibited; and there is a blue box for subsidies that are tied to programmes that limit production. There are also exemptions for developing countries (sometimes called an “S&D box”, including provisions in Article 6.2 of the agreement).
Source
What is in the amber box in the US SPS?