You have to deconstruct exactly what triggers the behavior to develop a correction plan, it is this deconstruction of the behavior, triggers, motivations that we as people have trouble with as we often assume things with out really thinking it through. We often fail to see what triggers a behavior and sometimes very innocent things we do or think are good ideas create end behaviors we don't want. Often as a result we jump to erroneous conclusions about what causes negative/bad behaviors.
Okay, so you need to determine exactly what the trigger for the behavior is. You suspect the buckets. I think you have already ruled out color. But you could try colour testing with poster board or construction paper or fabric to see how the roo responds just to color. You want to try and create the aggressive response on purpose so you can determine the actual elements that cause it. The main question seems to be is it you or the buckets the roo is responding to? Now I would see how they respond to a static empty bucket. Simply place a bucket on the ground in their space and then stand back and watch what they do. If they continue to go nuts at the bucket then it is the bucket related but if they ignore the bucket, then it is not just the bucket. Do they ignore the bucket and still go after you? Did they go to the bucket not get food and then come after you? Next I would do static bucket with feed in it and observe. Do they go after the bucket with food and ignore you? If they ignore you the aggression may be food reward based. If they ignore the bucket and you I would try setting up ways to cause an empty bucket to move (rope on it and try dragging, jerking, even moving it up and down some how and swinging it about, maybe hang it up on a rafter) you want to be removed from the bucket as it moves to see if it is the bucket moving by it's self causes a response. If they don't care about a moving bucket then you will have to really think hard about how you move, what is around you and the chickens, what reward is the rooster getting? The rooster has a motivation it is just not always obvious, and that is causing the problem.
Try and step back with your mind's eye and imagine as if you where watching yourself and the chickens during feeding, how do the birds behave before they recognize your presence, how do they behave after they see you, how do they approach you, how do you approach them, what is the reward? I do mean all the chickens not just the roo. All behavior is goal orientated... what are the posable goals of being aggressive towards you? Try and think of several. Try and come up with tests to rule out triggers or narrow down the goal, once you are pretty sure about the goal of the aggression really is then you can change behavior by not rewarding the rooster. How do the birds behave when you are not feeding them but they see you and know you are around?
Why go to all this trouble when killing the rooster is easier? You need to determine if you are accidentally training the roosters wrong & even the hens to do bad things or if it really is a "man eater" rooster you have. Part of this is to rule out if it is accidental oops training you may have done (you may have done everything right too), because if it is something innocent you are doing it will continue to be a problem and all your future roosters might learn the same behaviors. Which would be a bummer & frustrating.
Your goal is to be able to keep a well adjusted rooster that behaves well towards people.
Your rooster's goal could be everything from food, territory defense/hen defense, dominance over you (sees you as a threat to his position in flock or an uppity inferior) and more.
Remember ALL behavior is GOAL orientated.
