Top panel: Optical CMD of NGC 663, based on Gaia DR3 photometry (first panel). The red points represent the optical counterparts (Gaia DR3) of the UVIT FUV/NUV detections. Be stars with UV excess, Be stars without UV excess, and Be stars showing UV excess but not fitted with a double component SED are shown as green triangles, cyan squares, and blue pentagons, respectively. The MIST isochrones corresponding to an age of 25 Myr and metallicity [Fe/H] = -0.125 dex are overplotted as solid black lines for various values of A_V, ranging from 2.17 to 2.9 (from left to right), assuming a reddening of E(B-V) = 0.7 mag and a distance modulus of (m-M)_V = 11.86 mag. The second and third panels in the upper panel show the FUV-optical and NUV-optical CMDs created using the F154W and N279N passbands, respectively, for the confirmed members of the cluster. Median error bars are displayed in grey on the left side of FUV and NUV-optical CMDs. Bottom panel: CCDs in the FUV-F154W vs F154W, FUV-F169M vs F169M, and NUV-N279N vs N279N planes, respectively. The meaning of the symbols shown is provided in the top-left panel of the first column.