For all you wondering how he got the mane to glow, I'm guessing really bright colors with a small blur around them. The darkness of the picture and how much the shading reacts gives it the illusion of how bright it is. I'm sorry if I'm wrong, but it just looks that way to me, haha.
idk exactly how the artist does it, but just based on the picture i can guess since the not-so-bright colours are very dark, the colours pop well. also there has been an airbrushing tool used outside of the line art to give it the glowing effect