It's a unique and beautiful landscape any time of the year.
Its look depends mainly on agriculture, wheat specifically, since that's what's mainly grown there. In spring, following germination, it's a wonderful, uniform carpet of green. As the crops ripen, the colours differentiate and close to harvest time (August, I believe) you get golds with your greens.
Weather is, as always a big factor. Mid-summer weather tends to be pretty stable - high pressure and blue skies. Springtime is more variable.
Any way you choose, it's a crapshoot, but it's a great location. I suggest finding the high rez maps (MapPoint is good) and explore the smallest roads. There are hundreds. You could spend weeks there.