grass in hedgerow country was how many different colors i have this one burnt turf i used so far from woodland scenic people and then i have a regular green turf and i was wondering all burnt turf or could i mix them

I'd say experiment. Try mixing small amounts of different colors and see if it looks natural. You couls also put a patch of burnt in with regular to show more wear or a natural patch of dead grass.

If you take a look at grass and bushes they are one or two basic shades. However, with the sun and light and dirt and Nature it appears to have a variety of shades.
As AJ is mentioning - experiment. Try different combination and quantities etc. Keep the tone even (no bright next to dull [unless its a dead patch]) and keep the shades within the same color group.
There isn't one answer for this - whatever you like would probably work.