I was unable to find a table matching wavelengths to visible temperatures in a bit of searching. Closest I could find is the chromaticity diagram on Wikipedia's Black-body Radiation article, which puts 1000K around 0.7nm red light.

The WISE article lists 22μm as its longest wavelength, though that might no longer be attainable since WISE is out of coolant. If one can find out what blackbody temperature has its peak at 22μm, then we could maybe see how close to the edge of WISE's temperature range the 400C (673K) and -10C (263K) dwarves are.

https://en.m.wikipedia.org/wiki/Wide-field_Infrared_Survey_E...

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Edit: found it: https://commons.m.wikimedia.org/wiki/File:Blackbody_peak_wav...

Looks like 20μm is a bit below 200K, so if I'm interpreting this right, WISE should have had no temperature-related problem (leaving aside brightness) spotting a -10C brown dwarf.