Spectral energy distribution of two models with similar parameters except the C, N, and O abundances: the red line shows a model with C/H reduced by a factor three (top panel), N/H increased by a factor three (middle), and O/H reduced by a factor three (bottom) compared to the initial model in black. The other parameters are: T_eff = 5375 K, log g = 3.37, Y = 0.248. The gray solid lines indicate the transmission curves of the HST WFC3/UVIS F275W, F336W, F395N, F410M, F467M, and ACS/WFC F606W and F814W.