Mid-infrared color-color diagram of the known ρ Oph sources in blue and the new ones in red, including the control sample in gray, using the W1, W2, and W3 passbands from the WISE catalog. The sources comprising the second population (Pop 2) are marked by black symbols. An extinction vector in the K_S passband, labeled as A_K, is also included. The sources above the dashed line with W1 − W2 > 1.05−0.8 ⋅ (W2 − W3), are YSOs with IR excess due to a circumstellar disk (Class I or Class II), while those below the line are Class III YSOs.