I don't know enough about Excel.

What determines how much of the cell gets filled?

What about something like this.
If Years in Service cell = 0 the Estimated Current Value cell has no color.
If Years in Service cell = 1 the Estimated Current Value cell has 20% color.
If Years in Service cell = 2 the Estimated Current Value cell has 40% color.
If Years in Service cell = 3 the Estimated Current Value cell has 60% color.
If Years in Service cell = 4 the Estimated Current Value cell has 80% color.
If Years in Service cell > 4 the Estimated Current Value cell has 100% color.

Right now I have it if
Years in Service cell = 4 Estimated Current Value cell has gradient red to white.
If Years in Service cell > 4 Estimated Current Value cell has solid red.
Otherwise the cell has no color.

This provides a pretty good visual as to what is going out of service and what is out of service. I guess I could use different shades of red lighter to darker as things get older?