Having worked around color concrete for several years I would definitely suggest using a know brand of color. For me I would only use L.M. Scofield
http://www.scofield.com/decorativeconcrete.html .
There are several different products. I would say to go their web site and read about what they have. Here is the basics:
Integral color: This is a color powder that is added to the concrete mix (truck). Most ready mix plants carry Scofield and can quote your concrete with color. They will do everything (order and add it to the mix) this way you can have consistency over several trucks. There is one hitch with a small load 1-2cy with a short load the color will stick to the drum and you will not have the same color, so order in 5 yard increments.
Color hardener: This is a shake on color, added when the concrete is wet then toweled in when you finish the concrete. This is usually brighter color but will only be in the top ¼” of concrete. If you chip or scrape the floor the color will be gone.
Stains: These are a transparent stain and create a modeled finish. This is typically what you see in stores like Starbucks. You can add a couple of colors together and get some really good looking floors. This only penetrates the very top surface and will ware (and eventually can ware off).