The choice to wait until grass is dormant or not is a matter of preference when it comes to painting grass. Some people like to see the grass remain green as long and as much as possible. If so, many find that applying colorant at half rate just before dormancy is a great way to achieve that. Then, apply Endurant at full rate when in full dormancy and again at half rate during the transition back to the growing season. This leads to ideal results.
However, some have had great results just spraying once when turf has reached total dormancy.
When deciding whether to wait until grass is dormant or not Endurant Flex is a colorant that is often applied during the transition times. Lastly, multiple applications can lead to a smoother transition and more consistent color throughout the year. Ultimately, it's up to your budget and preference.