Color is far less important in the breed than the ability of the dog to perform with speed, ease, and stamina. Most dog handlers agree that it has little to do with age. Young dogs learn quickly what's expected of them when they are taken for a training run. But, like children, they can get grouchy and pick a fight with another dog when they become tired. Most teams are mixed, with both females and males.
Females make solid leaders.
They bond well with the males, and the males won't challenge them. Athletically and instinctively, they're equal. The differences become apparent in aggressiveness and endurance. Males are usually the more aggressive pullers while the females have greater endurance. A balanced team would then benefit from having both on it.