I just made a batch of peanut brittle. This was my first time making it, so I followed a tradition recipe. I used raw red skinned spanish peanuts for this. The peanuts were relatively smaller than average. I put the peanuts into the sugar mixture when it was at 235 F and cooked it to 290 F. I removed it from the heat and added the butter and soda and beat it to blend. As soon as the soda started foaming it had a greenish tint to the toffee/brittle mixture. It eventually dissipated and changed to a lighter brown color, but the bottom of the brittle was still greenish. Any suggestions as to why this happened and what I can do to prevent this again?