Representing time with colored spaces decreases information density. Green & red blocks aren't enough -- the primary data, the numbers, are still required labels, and are made smaller to accommodate the new elements.
Shrinking the primary data decreases visibility, so you, with decent eyesight, need to be closer. My grandmother will have an even harder time resolving it.
Visibility hasn't been addressed, but deserves to be in any conversation about signage.
Plus producing identically sized signs has economies of scale that variable sized ones likely won't counteract.