In some systems I do custom scripting to achieve this, but it’s buggy. I like my freshness colour scheme to follow the colours of leaves across the seasons. Light green is spring for fresh new tasks. Darker green means it’s time to do them, then they fade through light red (late) orange and yellow (review, revise or possibly cull), then brown (almost certainly irrelevant now and needing to be culled). Depending on the task, I set the dates for this to happen differently. Some tasks go stale faster than others.