The investors couldn't necessarily be sure how any given run would turn out, but they picked their own colors and hoped for the best. One run I have many marbles from turned out very dark because the plan was to only put in one portion of blue, but there was confusion and the blue was put in repeatedly. So some people got luckier than others.
But Dave McCullough and the investors learned by 2007 what kind of glass to add to the mix to get oxblood. That's when the experiments were started which led to the contract runs which would continue for many years after that, basically up to the time of Dave's death one year ago.