  In this study, we extend the dust-independent Hatzidimitriou (1991) relation
between cluster age and $d_{B-R}$ color difference between red giant branch
(RGB) and red clump (RC) to younger cluster ages. We perform membership
analysis on twenty-two open clusters using $\textit{Gaia}$ DR3 astrometry, then
compute the difference in color of red giant branch and red clump $d_{B-R}$
using $\textit{Gaia}$ photometry. We find that the trend derived from older
clusters does not extrapolate to younger ages and becomes double-valued. We
confirm that $d_{B-R}$ is independent of metallicity. Current stellar
evolutionary isochrones do not quantitatively reproduce the trend and
furthermore predict an increased color gap with a decrease in metallicity that
is not echoed in the data. Integrated light models based on current isochrones
exaggerate the color change over the $-0.5 <$ [Fe/H] $< 0$ interval at the
few-percent level.
