  Recent studies have indicated that the ratio between half-mass and half-light
radii, $r_{\rm mass} / r_{\rm light}$, varies significantly as a function of
stellar mass and redshift, complicating the interpretation of the ubiquitous
$r_{\rm light}- M_*$ relation. To investigate, in this study we construct the
light and color profiles of $\sim 3000$ galaxies at $1<z<2$ with $\log\,
M_*/M_\odot > 10.25$ using $\texttt{imcascade}$, a Bayesian implementation of
the Multi-Gaussian expansion (MGE) technique. $\texttt{imcascade}$ flexibly
represents galaxy profiles using a series of Gaussians, free of any a-priori
parameterization. We find that both star-forming and quiescent galaxies have on
average negative color gradients. For star forming galaxies, we find steeper
gradients that evolve with redshift and correlate with dust content. Using the
color gradients as a proxy for gradients in the $M/L$ ratio we measure half
mass radii for our sample of galaxies. There is significant scatter in
individual $r_{\rm mass} / r_{\rm light}$ ratios, which is correlated with
variation in the color gradients. We find that the median $r_{\rm mass} /
r_{\rm light}$ ratio evolves from 0.75 at $z=2$ to 0.5 at $z=1$, consistent
with previous results. We characterize the $r_{\rm mass}- M_*$ relation and we
find that it has a shallower slope and shows less redshift evolution than the
$r_{\rm light} - M_*$ relation. This applies both to star-forming and quiescent
galaxies. We discuss some of the implications of using $r_{\rm mass}$ instead
of $r_{\rm light}$, including an investigation of the size-inclination bias and
a comparison to numerical simulations.
