  We present $GalevNB$ (Galev for $N$-body simulations), an utility that
converts fundamental stellar properties of $N$-body simulations into
observational properties using the $GALEV$ (GAlaxy EVolutionary synthesis
models) package, and thus allowing direct comparisons between observations and
$N$-body simulations. It works by converting fundamental stellar properties,
such as stellar mass, temperature, luminosity and metallicity into
observational magnitudes for a variety of filters of mainstream
instruments/telescopes, such as HST, ESO, SDSS, 2MASS, etc.), and into spectra
that spans from far-UV (90 $\rm \AA$) to near-IR (160 $\rm \mu$m). As an
application, we use $GalevNB$ to investigate the secular evolution of spectral
energy distribution (SED) and color-magnitude diagram (CMD) of a simulated star
cluster over a few hundred million years. With the results given by $GalevNB$
we discover an UV-excess in the SED of the cluster over the whole simulation
time. We also identify four candidates that contribute to the FUV peak, core
helium burning stars, thermal pulsing asymptotic giant branch (TPAGB) stars,
white dwarfs and naked helium stars.
