The type of Hidden Power you will receive depends on if each IV is odd or even.
If you click on the following link:
And scroll down until you see all the Grass combinations. Basically, every 31 mea.s there has to be an odd number in that place, while every 30 needs to have an even number in that place.
But those are basically all the combinations for Grass. The 30s and 31s can be any even and odd numbers respectively to produce that type.
Hope I helped. :)
Sources: Above Link and Experience