More Question from a Total War Warhammer Newbie

Second round of questions I just can't seem to find answers to:

When using selecting artillery and aiming it at something the various arcs that appear have different colors: Red, Yellow, Blue, and Grey are what I have seen so far. What do the various colors mean?

Does the equipment a Hero/Agent unit have affect the chances of a successful assassination?

When a spell mis-casts does it outright kill the caster or just do some amount of damage? (I would have tried this myself but enemy agents have decided I am not permitted to have any wizards and assassinate them all as they come out)

What affects does the various levels of stamina have on units? I did find a video on Total War Rome 2 for this one but the stamina levels seem to be slightly different now.

Final question for this round: Are there any good guides that would have good info for basically everything in Total War Warhammer so I can stop searching for an hour every time I have a question that the game?