Super glad you like that call!
There's not as much difference from Red to Green. I don't notice any real difference in them when I have them in the same wood. Both will give you the higher raspier pitch and tone then what you'll get out of the grey slate. I really am pleased with the red and the green slate I'm getting. My only issue has been with the purple. I ordered one order of it to check it out and the quality of it was very sub-par. The overall diameter with all over the place and the thickness was equally inconsistent. I won't be making any more purple slates this year, but I'm very happy with the red and the green and they both have a very similar sound.
-Paul Durham