Yellow, red, and purple colors are signs of plant stress from things like rapid temp change, nutrient deficiencies, lack of oxygen, ect…..The next time you go back I would take a couple bags of 17-`17-17 and go ahead and get something out for now to give the plants a boost. The new plants will be growing in the same nutrient deficient soil that caused that poor looking wheat. While your there pull a soil sample and send it in to have tested. It’s something like $7 at Auburn. I’d also recommend taking back a bag of milo with you and throw some of it out before the next rain. It would be a good thing if you have some type of grass specie growing in there this summer. “Grass” species are our biggest suppliers of organic matter….high C/N ratio. For winter and summer try to include 3 components of your mix……grass, broadleaf, legume. They all play a role in making the whole cycle function properly.