Normalised UCD spectra in the three EDFs. From the top to the bottom are UCDs from EDFs North, Fornax, and South, respectively. The VLT/X-shooter and GTC/EMIR spectra were smoothed with a 31 and 5-pixel-size window, respectively. All the spectra were classified into spectral subclasses, and the best-fit templates are plotted in grey (left panel). We Euclidised the spectra and the classifications remain consistent within 0.5 subclasses (right panel).