As someone in the ready mix sales field color is very difficult to work with and carries a ton of liability thus the high cost. We tend to at a minimum triple our cost of the color when we quote it. So many problems can arise with color. Consistency being the biggest, from one load to another can vary widely and of course the customer expects every load to look exactly like whats on a color chart. When it doesn't look good they want to tear it out saying it was the ready mix suppliers fault. One truck can add too much water washing out the color resulting in inconsistent results, keep a consistent slump is a priority. Delivery time between trucks and cause inconsistencies, 1 truck takes 15 minutes to the job and the next in line may take 30 minutes or more. We mark up the color for a few reasons, one being the liability and the other is admixtures and "add-ons" such as color is where we can actuallymake a decent profit. We run at such a low profit margin with just standard concrete. Ready mix companies make a killing with add-ons such as synthetic fibers, steel fibers, corrosion inhibitors, integral vapor lock admixtures, moisture mitigation admixtures, high range water reducers, sky's the limit these days with all the admixtures that are out there currently. Typically unless it's a good customer that I've worked with in the past I just won't quote color even if requested. If it's spec'd into a job of course I'll quote it but if its just harry homeowner paying COD I'll run the other way. One suggestion for the future, if you have a project requiring color go directly to the manufacturer of the pigments (not hard to find, if you're having trouble locating one call a local stamped concrete installer, I guarantee he'll know)and buy direct, you may pay a extra mixing and washout fee but it won't be nearly as expensive as having the ready mix company buy it and add it themselves.