colored concrete is awesome if done right - but we went through a nightmare with the stuff. A few things we learned the hard way after hiring "experienced professionals".
we ran into this issue with colored concrete counter tops that were poured in place.
1. the amount of dye you use is very important - too much dye will keep the concrete from sticking to itself, so it will never set
2. screeding/troweling the top changes the color - a lot. this makes the color way off of any samples, and color matching just about impossible if you have to patch any imperfections. patches will be dark and the trowled parts will be light. We are talking about the difference between maroon and a light pink if you order the dye for maroon.
3. the dye is nasty and stains everything. natural colors are not as noticeable., but my driveway/yard/rocks/trees wash are all still stained blue from the mixing/cleanup that those a$$clowns did.
they ended up pouring 4 times, ruined our cabinets, and the counter tops still look like S%$.T