Concrete Color

We have recently concreted a driveway, the concrete was delivered to the site in two parts on two different days and under similar weather conditions.  Although the mix was of the same consistency a number 124 50 slump, it would appear that when it has set it has set in two different colours.

Please can you advise us of the possible reasons for this occurring, and is there any way of toning the colours in so they match, as at present one area is a different colour to the other.

Thank You.
This is common, even though I would not expect a large difference in two loads on one day. The reasons may be any of the following:

More cement -- darker
More water -- lighter
Different aggregate - depending on its color

Small variations are common.

One thing that may have happened is that one of the loads was not what you ordered. Usually, the builder orders concrete with minimum strength properties.  In a driveway, that would be the most basic mix.  If, for some reason, the ready-mixed concrete supplier had an extra load of concrete sitting around (someone canceled) he might send it to you instead of dumping it. You may be getting concrete that is much better than what you ordered, but it will look different. As far as building codes are concerned this may be fine, but it should be easy to find out from the delivery tickets.

Another possibility is a different finishing process.  If the finish is done late, the earlier concrete had time to dry a little and the finish may appear lighter.

The best thing to do is probably to wait a while and let the concrete mature. The color difference may disappear. You may also call it "concrete with character" and live with it.  Or, you can ask the builder/supplier to fix it - which may be more trouble than you need.

Good luck