Hair colour
Emo hair is whatever colour you want - no rules. Blonde, rich brown, it's all good. But in place of rules emo has guidelines, and emo hair is frequently dyed black. It can be highlighted with brighter colours (blonde, auburn, red, blue, pink) to give more definition and edge. Highlighting the tips in bright colours - or going for minimal streaks - works well.
The emo fringe
An emo fringe should cover half your face, even if you sometimes hold it back with pretty plastic hair clips. If you're doing a home emo cut, make sure your hair parting is heavily to the left or right before you cut. Then your fringe will be good and heavy. Fringes are important in an emo hair cut - they shield you from the world, masking your identity, so you can reveal yourself to the world a little at a time.
Keep it asymetric
What you're looking for is a jagged style with different layers and cuts. An emo hairstyle has real shape and unusual proportions. Cutting your hair with a razor comb will definitely achieve this, especially if you've never done a home cut before. You can get your hair (long or short) to be asymetric through a styled cut or through spiking it with product. Like the emotional music that initially spawned the emo scene, emo hair should also be expressive and change frequently - emotion expressed in hair. It's proper art, when you think about it.
Hair colour
Keep it asymetric