NUV − J versus J − W1 for stars in the sample. Blue dots refer to the full sample of stars toward Orion and red dots refer to extragalactic sources according to the used criteria (see text). Open circles are identified TTSs in the SIMBAD database. The A_V = 1 mag reddening vector is shown with an arrow. Dashed line indicates the region used for a first selection of TTS candidates.