Three things I forgot to mention:
1) Standard Newtonian laws apply here. You throw luxin forward, you're pushed back. The more luxin you throw and the faster you throw it, the greater the backward force.
2) Mirrors. Upon contact, mirrors can diminish luxin's power. In battle, there are usually a lot of folks in mirror armour to counter luxin projectiles. However, like normal armour, mirrors do not completely negate luxin, only reduce its strength.
3) Obsidian. Obsidian has the power to leech the colours from a drafter, but only if 2 conditions are met (I think). I can't remember the conditions, and I don't have the books with me to re-read, and the wiki is spoilery, so @Argenti, since you've read the entire wiki, can you tell me what they are, without mentioning anything about