  Optical and near-infrared spectroscopy of the newly discovered peculiar L
dwarf 2MASS J11263991-5003550 are presented. Folkes et al. identified this
source as a high proper motion L9+/-1 dwarf based on its strong H2O absorption
at 1.4 micron. We find that the optical spectrum of 2MASS J1126-5003 is in fact
consistent with that of a normal L4.5 dwarf with notably enhanced FeH
absorption at 9896 A. However, its near-infrared spectrum is unusually blue,
with strong H2O and weak CO bands similar in character to several recently
identified ``blue L dwarfs''. Using 2MASS J1126-5003 as a case study, and
guided by trends in the condensate cloud models of Burrows et al. and Marley et
al., we find that the observed spectral peculiarities of these sources can be
adequately explained by the presence of thin and/or large-grained condensate
clouds as compared to normal field L dwarfs. Atypical surface gravities or
metallicities alone cannot reproduce the observed peculiarities, although they
may be partly responsible for the unusual condensate properties. We also rule
out unresolved multiplicity as a cause for the spectral peculiarities of 2MASS
J1126-5003. Our analysis is supported by examination of Spitzer mid-infrared
spectral data from Cushing et al. which show that bluer L dwarfs tend to have
weaker 10 micron absorption, a feature tentatively associated with silicate
oxide grains. With their unique spectral properties, blue L dwarfs like 2MASS
J1126-5003 should prove useful in studying the formation and properties of
condensates and condensate clouds in low temperature atmospheres.
