Context :

Aims : We pose the question of how much information on the atmospheric parameters of late-type stars can be retrieved purely from color information using standard photometric systems .

Methods : We carried out numerical experiments using stellar fluxes from model atmospheres , injecting random noise before analyzing them .
We examined the presence of degeneracies among atmospheric parameters , and evaluated how well the parameters are extracted depending on the number and wavelength span of the photometric filters available , from the UV GALEX to the mid-IR WISE passbands .
We also considered spectrophotometry from the Gaia mission .

Results : We find that stellar effective temperatures can be determined accurately ( \sigma \sim 0.01 dex or about 150 K ) when reddening is negligible or known , based merely on optical photometry , and the accuracy can be improved twofold by including IR data .
On the other hand , stellar metallicities and surface gravities are fairly unconstrained from optical or IR photometry : \sim 1 dex for both parameters at low metallicity , and \sim 0.5 dex for [ Fe/H ] and \sim 1 dex for \log g at high metallicity .
However , our ability to retrieve these parameters can improve significantly by adding UV photometry .
When reddening is considered a free parameter , assuming it can be modeled perfectly , our experiments suggest that it can be disentangled from the rest of the parameters .

Conclusions : This theoretical study indicates that combining broad-band photometry from the UV to the mid-IR allows atmospheric parameters and interstellar extinction to be determined with fair accuracy , and that the results are moderately robust to the presence of systematic imperfections in our models of stellar spectral energy distributions .
The use of UV passbands helps substantially to derive metallicities ( down to [ Fe/H ] \sim - 3 ) and surface gravities , as well as to break the degeneracy between effective temperature and reddening .
The Gaia BP/RP data can disentangle all the parameters , provided the stellar SEDs are modeled reasonably well .