  We suggest using a two-color evanescent light field around a
subwavelength-diameter fiber to trap and guide atoms. The optical fiber carries
a red-detuned light and a blue-detuned light, with both modes far from
resonance. When both input light fields are circularly polarized, a set of
trapping minima of the total potential in the transverse plane is formed as a
ring around the fiber. This design allows confinement of atoms to a cylindrical
shell around the fiber. When one or both of the input light fields are linearly
polarized, the total potential has two local minimum points in the transverse
plane. This design allows confinement of atoms to two straight lines parallel
to the fiber axis. Due to the thin thickness of the fiber, we can use
far-off-resonance fields with substantially differing evanescent decay lengths
to produce a net potential with a large depth, a large coherence time, and a
large trap lifetime. For example, a 0.2-$\mu$m-radius silica fiber carrying 30
mW of 1.06-$\mu$m-wavelength light and 29 mW of 700-nm-wavelength light, both
fields are circularly polarized at the input, gives for cesium atoms a trap
depth of 2.9 mK, a coherence time of 32 ms, and a recoil-heating-limited trap
lifetime of 541 s.
