Bright colours in nature usually signify danger due to the fact that if they are showing so much colour then they have no fear and must be dangerous / poisonous. There are, of course, many exceptions to the rule. Study a martial arts champion and make a comparison against a d1ckhead. You will usually find the champion displays an air of confidence without being "in your face", whilst the other is loud and bolshy. Thus the saying, it is the quiet ones you have to watch. Again, there are exceptions to the rule.