  AIMS: We aim to evaluate the near-infrared colors of brown dwarfs as observed
with four major infrared imaging space observatories: the Hubble Space
Telescope (HST), the James Webb Space Telescope (JWST), the Euclid mission, and
the WFIRST telescope.
  METHODS: We used the SPLAT SPEX/ISPEX spectroscopic library to map out the
colors of the M-, L-, and T-type dwarfs. We have identified which color-color
combination is optimal for identifying broad type and which single color is
optimal to then identify the subtype (e.g., T0-9). We evaluated each
observatory separately as well as the narrow-field (HST and JWST) and
wide-field (Euclid and WFIRST) combinations.
  RESULTS: The Euclid filters perform poorly typing brown dwarfs and WFIRST
performs only marginally better, despite a wider selection of filters. WFIRST's
W146 and F062 combined with Euclid's Y-band discriminates somewhat better
between broad brown dwarf categories. However, subtyping with any combination
of Euclid and WFIRST observations remains uncertain due to the lack of medium
or narrow-band filters. We argue that a medium band added to the WFIRST filter
selection would greatly improve its ability to preselect brown dwarfs its
imaging surveys.
  CONCLUSIONS: The HST filters used in high-redshift searches are close to
optimal to identify broad stellar type. However, the addition of F127M to the
commonly used broad filter sets would allow for unambiguous subtyping. An
improvement over HST is one of two broad and medium filter combinations on
JWST: pairing F140M with either F150W or F162M discriminates very well between
subtypes.
