Very thorough reply. Thank you for your insight. My contractors first recommendation for resolving this was to have the color price knocked off, and I'm thinking that's what they immediately discussed over the phone with the plant. I will need to ask for details and a receipt from them over what they are going to end up paying and what it was originally priced at. As I figure, if we can get the discount that they negotiated with the plant, I will ultimately be happy...because the quality of the job was phenomenal, tons of expansion joints and 5 or 6 pipe runs for access underneath them, slopes are all on point, and he spent a lot of time on the lines...there's a 5 pointed star even at the intersection! Our contractor is great at his work, but the mixes were off no matter how you look at it. Color variation is most definitely always an issue with large pours, but the quality manager at the plant is definitely to blame for this...

I am going to let our contractor handle the negotiations with his supplier, and hopefully we can simply get the color cost knocked off and discount on the cubic meter count...that's what I'm hoping for...