nevermind. I was too tired last night. This was a stupid question:
SolidColorBrush brush = (SolidColorBrush)rect[ii].Fill;
brush.Color = Color.FromArgb(255, colorTmp, colorTmp, colorTmp);
SolidColorBrush brush = (SolidColorBrush)rect[ii].Fill;
brush.Color = Color.FromArgb(255, colorTmp, colorTmp, colorTmp);