  Determining the Galactic distribution and numbers of massive stars, such as
Wolf-Rayet stars (WRs), is hampered by intervening Galactic or local
circumstellar dust obscuration. In order to probe such regions of the Galaxy we
can use infrared observations, which provide a means for finding such hidden
populations through the dust. The availability of both 2MASS and
Spitzer/GLIMPSE large-scale survey data provides infrared colours from 1.25 to
8$\mu$m for a large fraction of the inner Galactic plane. In 2005 we initiated
a pilot study of the combined set of infrared colours for two GLIMPSE fields
and showed that WRs typically occupy a sparsely populated region of the colour
space. We followed up 42 of our WR candidates spectroscopically in the
near-infrared, and with limited additional observations of some of these
candidates in the optical. Six new WRs, four late-type WN and two late-type WC
stars, were discovered as a result. Of the remaining $\sim$86% of the sample,
five appear to be O-type stars. 21 stars are likely of type Be, and 10 stars
appear to be of late-type, or possibly young stellar objects, which have
"contaminated" the infrared color space. The survey is generally unbiased
towards clusters or field stars, and the new WRs found are in both the field
and in and around the RCW 49 region (including cluster Westerlund 2). In this
work, and in our other recent work, we show that the infrared broad-band
colours to be the most efficient means of identifying (particularly,
dust-obscured) candidate massive stars, notably WRs.
