When determining the furthest objects currently observable, what measurement is the definitive yardstick?

Answer

The sheer magnitude of the redshift value

To determine the furthest objects, the magnitude of the measured redshift value eclipses any information about the galaxy's intrinsic color, as it relies on precisely measuring spectral line shifts.

When determining the furthest objects currently observable, what measurement is the definitive yardstick?
galaxiesastronomyDistanceredshift