We prefer the masonry colorant. In spite of your best efforts there will be a little bit of color variations from batch to batch. As the surface weathers this seems to quickly even out, unless it is quite drastic. One option is to cover most of the area with stucco and then come back over it with a light color coating to even out any variations. If color is absolutely important, the best thing to do is apply the stucco and then cover it with a concrete stain.
Concrete stains are available at any paint supply house.
It generally takes two or more coats of stain to cover the stucco evenly. It is to be applied at least 10 minutes before applying the stucco. It may be applied up to a week earlier if it is not subject to frost, rain, or heavy dew. I 200 to 250 lbs of Sand. This can be Silica, Mortar Sand or Fine Play Sand.