  We highlight differences in spectral types and intrinsic colors observed in
pre-main sequence (pre-MS) stars. Spectral types of pre-MS stars are
wavelength-dependent, with near-infrared spectra being 3-5 spectral sub-classes
later than the spectral types determined from optical spectra. In addition, the
intrinsic colors of young stars differ from that of main-sequence stars at a
given spectral type. We caution observers to adopt optical spectral types over
near-infrared types, since Hertzsprung-Russell (H-R) diagram positions derived
from optical spectral types provide consistency between dynamical masses and
theoretical evolutionary tracks. We also urge observers to deredden pre-MS
stars with tabulations of intrinsic colors specifically constructed for young
stars, since their unreddened colors differ from that of main sequence dwarfs.
Otherwise, V-band extinctions as much as ~0.6 mag erroneously higher than the
true extinction may result, which would introduce systematic errors in the H-R
diagram positions and thus bias the inferred ages.
